Further Proof & Reasoning (DP IB Maths: AA HL)

Topic Questions

3 hours38 questions
1
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5 marks

Prove that there is no x element of straight real numbers such that  begin mathsize 16px style negative fraction numerator 2 over denominator x minus 2 end fraction equals x minus 3 end style.

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2
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4 marks

Using the method of proof by contradiction, prove that square root of 7 is irrational.

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3
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4 marks

Using mathematical induction, prove that 6 to the power of n minus 1 is divisible by 5 for n element of straight integer numbers comma space n greater or equal than 1.

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4a
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1 mark

The nth triangular number is given by the formula u subscript n equals 1 half n open parentheses n plus 1 close parentheses.

Write down the first five triangular numbers.

4b
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2 marks

Prove by exhaustion that the first five triangular numbers are all factors of 180.

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5
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8 marks

Determine, with appropriate reasoning, whether the following statements are true or false: 

(i)
Given n element of straight integer numbersand n squared is divisible by 4, then n is divisible by 4.

 

(ii)
Given n element of straight integer numbers then n squared minus 1 is a prime number.

 

(iii)
Given n element of straight integer numbersand n squared is divisible by 3, then n is divisible by 3.

 

(iv)
Given an integer is a multiple 8 and 6 then it is a multiple of 48.

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6
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3 marks

Prove that x squared minus 3 x plus 3 is positive for all real values of x.   

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7a
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2 marks

Show that open parentheses 3 n plus 2 close parentheses squared minus open parentheses n plus 2 close parentheses squared equals 8 n squared plus 8 n, where n element of straight integer numbers.

7b
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2 marks

Hence, or otherwise, prove that left parenthesis 3 n plus 2 right parenthesis squared minus open parentheses n plus 2 close parentheses to the power of 2 end exponent is a multiple of 8.

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8
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3 marks

Prove that open parentheses a minus b close parentheses squared minus open parentheses a plus b close parentheses squared equals negative 4 a b.

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9
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3 marks

Prove that open parentheses 4 x minus 1 close parentheses open parentheses 2 x plus 3 close parentheses minus open parentheses 2 x plus 1 close parentheses squared equals 2 open parentheses 2 x minus 1 close parentheses open parentheses x plus 2 close parentheses.

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10
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6 marks

Prove by mathematical induction 3 to the power of n greater or equal than 1 plus 2 n comma given n greater or equal than 0.

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11
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6 marks

Prove by mathematical induction that if begin mathsize 16px style y equals fraction numerator 1 over denominator 1 minus x end fraction end style  then begin mathsize 16px style fraction numerator d to the power of n y over denominator d x to the power of n end fraction equals fraction numerator n factorial over denominator left parenthesis 1 minus x right parenthesis to the power of n plus 1. end exponent end fraction end style

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12
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6 marks

Prove by induction that

large capital sigma from r equals 1 to n ofr squared equals 1 over 6 n open parentheses n plus 1 close parentheses open parentheses 2 n plus 1 close parentheses

for all values of n comma space n element of straight integer numbers to the power of plus.

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13
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4 marks

Given z equals x plus y i

(i)
prove that z z to the power of asterisk times equals open vertical bar z close vertical bar open vertical bar z to the power of asterisk times close vertical bar,
(ii)
prove that, for x greater or equal than 0, arg open parentheses z close parentheses plus arg open parentheses z to the power of asterisk times close parentheses equals 0.

 

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1
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4 marks

Prove that the equation k x squared minus 2 open parentheses k plus 1 close parentheses x minus 3 k equals 0  has distinct real solutions for all values of k , where k element of straight real numbers.

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2
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4 marks

Prove by mathematical induction that  9 to the power of 2 n end exponent minus 1 comma space n element of straight integer numbers comma space n greater or equal than 1 is divisible by 16.

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3
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4 marks

Prove by contradiction that square root of 10 is irrational.

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4
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4 marks

Prove by exhaustion that the sum of two consecutive square numbers between 100 and 200 is an odd number.

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5
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4 marks

The three statements below are false.

In each case verify the statement is false by use of a counter example and state an alternative domain that would make the statement true. 

(i)
n squared greater than 2 n comma space space n element of straight integer numbers to the power of plus
 
(ii)
2 to the power of n minus 1 is a prime number for n element of straight natural numbers comma space 1 less than n less or equal than 4. 

(iii)
5 to the power of n greater than 3 to the power of n plus 4 to the power of n comma space n element of straight integer numbers to the power of plus

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6
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6 marks

Use mathematical induction to prove that the nth derivative of the function f open parentheses x close parentheses equals 5 over x is  given by

 fraction numerator 5 open parentheses negative 1 close parentheses to the power of n n factorial over denominator x to the power of open parentheses n plus 1 close parentheses end exponent end fraction 

for all integers, n, where n greater or equal than 1.

 

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7
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6 marks

Prove that a squared minus 8 b minus 11 not equal to 0 if a comma space b element of straight integer numbers.

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8
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4 marks

The product of three consecutive integers is added to the middle integer. 

Prove that the result is a perfect cube.

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9
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6 marks

Prove by mathematical induction, that for n element of straight integer numbers to the power of plus,

1 plus 2 open parentheses 1 half close parentheses plus 3 open parentheses 1 half close parentheses squared plus 4 open parentheses 1 half close parentheses cubed plus... plus n open parentheses 1 half close parentheses to the power of n minus 1 end exponent equals 4 minus fraction numerator n plus 2 over denominator 2 to the power of n minus 1 end exponent end fraction

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10
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6 marks

Use a contradiction to prove that the difference between a rational number and an irrational number is irrational.

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11
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4 marks

Prove that there are no non-zero real values of a  and b such that  open parentheses a plus b straight i close parentheses squared equals a plus b straight i.

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12
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6 marks

Prove by mathematical induction that if f open parentheses x close parentheses equals x e to the power of 2 x end exponent then f to the power of open parentheses n close parentheses end exponent open parentheses x close parentheses equals open parentheses 2 to the power of n x plus n 2 to the power of n minus 1 end exponent close parentheses e to the power of 2 x end exponent .

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13
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6 marks

Prove by mathematical induction that

open parentheses cos space theta minus straight i space sin space theta close parentheses to the power of n equals cos open parentheses n theta close parentheses minus straight i space sin open parentheses n theta close parentheses comma space for space all space n element of straight integer numbers to the power of plus

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1
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4 marks

Prove that there are no real values of k such that the equation k x open parentheses 1 minus x close parentheses equals 3 x squared minus 1 has no real solutions.

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2
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6 marks

Prove that 2 to the power of n plus 2 end exponent plus 3 to the power of 3 n end exponent is divisible by 5 for n element of straight integer numbers comma space n greater or equal than 0.

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3
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4 marks

Prove that there are an infinite number of prime numbers.

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4
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3 marks

523 and 541 are prime numbers.

Prove by exhaustion that these are consecutive prime numbers.

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5
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3 marks

Three of the four statements below are false.

Eliminate the false statements by providing a counter example and thus deduce the true statement.

(i)
open parentheses x minus 1 close parentheses squared not equal to open parentheses x plus 1 close parentheses squared comma space space x element of straight real numbers.
(ii)
Every open parentheses 4 n close parenthesesth triangular number is even, n element of straight natural numbers.
(iii)
2 space ln space x greater than ln space 2 x comma space x element of straight real numbers comma space x greater than 0.
(iv)
The product of any two distinct positive integers is greater than their sum.

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6
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5 marks

Prove that the equation 5 x to the power of 4 plus 15 x cubed minus 20 x squared minus 4 equals 0 has no integer solutions.

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7a
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2 marks

The function f open parentheses n close parentheses is given as f open parentheses n close parentheses equals n cubed plus n squared plus 17  where n is an integer.

Find f open parentheses 1 close parentheses comma space f open parentheses 2 close parentheses and f open parentheses 3 close parentheses.

7b
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2 marks

Prove that f open parentheses n close parentheses is not prime for all values of n.

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8a
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2 marks

Write down a comma space b comma space cand d from smallest to largest, given a comma space b comma space c comma space d element of straight real numbers and c greater than d comma space a less than d and a greater than b.

8b
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3 marks

Write down p comma space q comma space r and s from smallest to largest, given p comma space q comma space r comma space s element of straight real numbers and

p greater than q
r minus s less than q minus p
p plus q equals r plus s.
8c
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3 marks

Prove fraction numerator x over denominator 1 plus x end fraction less than fraction numerator x over denominator 1 plus y end fraction comma space x comma space y element of straight real numbers,  given 0 less or equal than x less than y.

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9a
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3 marks

Show that the derivative of y equals x e to the power of negative x end exponent is

fraction numerator d y over denominator d x end fraction equals e to the power of negative x end exponent open parentheses 1 minus x close parentheses.
9b
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7 marks

Prove, by mathematical induction, that for n greater or equal than 1 comma

fraction numerator straight d to the power of n over denominator straight d x to the power of n end fraction equals e to the power of negative x end exponent open square brackets open parentheses negative 1 close parentheses to the power of n minus 1 end exponent n plus open parentheses negative 1 close parentheses to the power of n x close square brackets

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10
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6 marks

Given that the graph of  y equals x to the power of 4 minus 10 x cubed plus 37 x squared minus 60 x plus 36 touches the x-axis at the point with coordinates open parentheses 2 comma 0 close parentheses , prove that y greater or equal than 0 for all real values of x .

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11
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7 marks

Prove that open square brackets r open parentheses cos space theta minus i sin theta close parentheses close square brackets to the power of n equals r to the power of n open square brackets cos open parentheses n theta close parentheses minus i sin open parentheses n theta close parentheses close square brackets,  for all n element of straight integer numbers to the power of plus  .

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12
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7 marks

Proof by Induction that

sum from r equals 1 to n of r open parentheses r squared minus 6 close parentheses equals 1 fourth n open parentheses n plus 1 close parentheses open parentheses n plus 4 close parentheses open parentheses n minus 3 close parentheses

for all positive integer values of n.

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