Simple Proof & Reasoning (DP IB Analysis & Approaches (AA): HL): Exam Questions

3 hours34 questions
13 marks

Prove that left parenthesis 4 x minus 1 right parenthesis left parenthesis 2 x plus 3 right parenthesis minus left parenthesis 2 x plus 1 right parenthesis squared equals 2 left parenthesis 2 x minus 1 right parenthesis left parenthesis x plus 2 right parenthesis.

23 marks

Prove that left parenthesis a minus b right parenthesis squared minus left parenthesis a plus b right parenthesis squared equals negative 4 a b.

33 marks

Prove that the sum of any three consecutive integers is a multiple of 3.

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2 marks

Prove that x squared plus 2 greater or equal than 2 for all values of x.

53 marks

 Prove that the square of an even number is a multiple of 4.

6a1 mark

Factorise n squared plus 3 n plus 2.

6b1 mark

Hence show that n cubed plus 3 n squared plus 2 n equals n left parenthesis n plus 1 right parenthesis left parenthesis n plus 2 right parenthesis.

6c2 marks

Given that n is even, write down whether open parentheses n plus 1 close parentheses and open parentheses n plus 2 close parentheses are odd or even.

6d2 marks

Hence deduce whether n cubed plus 3 n squared plus 2 n is odd or even. Justify your answer.

7a2 marks

Show that left parenthesis 3 n plus 2 right parenthesis squared minus left parenthesis n plus 2 right parenthesis squared8 n squared plus 8 n, where n element of straight integer numbers.

7b2 marks

Hence, or otherwise, prove that left parenthesis 3 n plus 2 right parenthesis squared minus left parenthesis n plus 2 right parenthesis squared is a multiple of 8.

83 marks

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

94 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.

108 marks

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

(i)  Given n element of straight integer numbers and 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 numbers and 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.

14 marks

Show that fraction numerator 1 over denominator n plus 1 end fraction plus fraction numerator 1 over denominator n squared plus n end fraction equals 1 over n.

24 marks

Forspace f left parenthesis x right parenthesis equals x squared minus 10 x plus 17, prove thatspace f left parenthesis x right parenthesis greater or equal than negative 8 for all values of x.

35 marks

Prove that the exterior angle in any triangle is equal to the sum of the two opposite interior angles. You may use the diagram below to help.

q3-1-4-ib-aa-sl-proof-and-reasoning
44 marks

Consider the functionspace f left parenthesis x right parenthesis equals 5 x squared plus 4 x plus 1. Show thatspace f open parentheses x close parentheses is positive for all values of x.

54 marks

Consider two consecutive positive integers, n and n plus 1.

Show that the difference of their squares is equal to the sum of the two integers.

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4 marks

Prove that left parenthesis 2 q minus 1 right parenthesis left parenthesis q minus 3 right parenthesis minus 3 left parenthesis q minus 4 right parenthesis squared equals negative q squared plus 17 q minus 45.

74 marks

Prove that the square of an odd number is always odd.

84 marks

Prove that the sum of the squares of any two consecutive odd integers is even.

94 marks

Prove that the sum of any three consecutive even numbers is a multiple of 6.

104 marks

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

Prove that the result is a perfect cube.

114 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.

124 marks

The three statements below are false.

In each case verify the statement is false by use of a counterexample 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

1a3 marks

(i) Prove that

fraction numerator a over denominator open parentheses b over c close parentheses end fraction equals fraction numerator a c over denominator b end fraction

(ii) Specify any cases for which the relation in part (a)(i) is not valid.

1b2 marks

Prove that left parenthesis p minus q right parenthesis squared equals left parenthesis q minus p right parenthesis squared for all numbersspace p and q.

24 marks

Prove that the product of two odd numbers is odd.

35 marks

The sum of squares of two consecutive integers is 313.  Find the possible values of the integers.

45 marks

Prove that the sum of the cubes of any two consecutive odd integers is divisible by four.

5a4 marks

Prove that fraction numerator a squared minus a minus 6 over denominator a plus 4 end fraction cross times fraction numerator a squared minus 16 over denominator a squared plus 2 a end fraction equals a minus 7 plus 12 over a.

5b1 mark

State any values of a for which this mathematical statement does not hold true.

64 marks

Prove that there are no integersspace p and q that satisfy the equation

4 p squared minus q squared equals 49

78 marks

Prove the binomial coefficient identity 

open parentheses table row n row k end table close parentheses equals open parentheses table row cell n minus 1 end cell row k end table close parentheses plus open parentheses table row cell n minus 1 end cell row cell k minus 1 end cell end table close parentheses.

88 marks

Prove that the sum of all integers between 600 and 1400 (inclusive) that are not divisible by 7 is equal to 685   885.

9a2 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.

9b3 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.

9c3 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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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 .

113 marks

Three of the four statements below are false.

Eliminate the false statements by providing a counterexample 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.

12a2 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.

12b2 marks

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