Proof & Reasoning (DP IB Maths: AA SL)

Exam Questions

2 hours25 questions
1
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3 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.

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2
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3 marks

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

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3
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3 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.

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4
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3 marks

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

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5
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2 marks

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

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6
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3 marks

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

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7a
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1 mark

Factorise n squared plus 3 n plus 2.

7b
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1 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.

7c
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2 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.

7d
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2 marks

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

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8a
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2 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.

8b
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2 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.

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1
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4 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.

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2
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4 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.

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3
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5 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

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4
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4 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.

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5
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4 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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6
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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.

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7
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4 marks

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

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8
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4 marks

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

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9
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4 marks

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

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1a
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3 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.
1b
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2 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.

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2
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4 marks

Prove that the product of two odd numbers is odd.

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3
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5 marks

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

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4
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5 marks

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

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5a
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4 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.

5b
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1 mark

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

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6
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4 marks

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

4 p squared minus q squared equals 49

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7
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8 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.

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8
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8 marks

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

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