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Cambridge Maths Academy
P2 §1.7 Review exercise for chapter 1 본문
P2 §1.7 Review exercise for chapter 1
Cambridge Maths Academy 2022. 6. 28. 21:35Pure mathematics Year 2
Table of contents
- Edexcel P2 Review exercise 1 Q1-10
1. Edexcel P2 Review exercise 1 Q1-10
Question 1. (E/P) Prove by contradiction that there are infinitely many prime numbers. [4 marks](Relevant section: P2 §1.1 Proof by contradiction.)
(Edexcel 2017 Specifications, P2 Review exercise 1 Q1.)
Solution.
Question 2. (E/P) Prove that the equation x2−2=0 has no rational solutions. You may assume that if n2 is an even integer then n is also an even integer. [4 marks](Relevant section: P2 §1.1 Proof by contradiction.)
(Edexcel 2017 Specifications, P2 Review exercise 1 Q2.)
Solution.
Question 3. (E) Express 4xx2−2x−3+1x2+x as a single fraction in its simplest form. [4 marks](Relevant section: P2 §1.2 Algebraic fractions.)
(Edexcel 2017 Specifications, P2 Review exercise 1 Q3.)
Solution.
Question 4. (P) f(x)=1−3x+2+3(x+2)2,x≠−2.(a) Show that f(x)=x2+x+1(x+2)2,x≠−2
(a) Show that x2+x+1>0 for all values of x, x≠−2.
(c) Show that f(x)>0 for all values of x, x≠−2.
(Relevant section: P2 §1.2 Algebraic fractions.)
(Edexcel 2017 Specifications, P2 Review exercise 1 Q4.)
Solution.
(b) By completing the square, x2+x+1=(x+12)2−14+1=(x+12)2+34≥34>0.◻
(c) This gives f(x)=x2+x+1(x+2)2=(x+12)2+34(x+2)2 For x≠−2, since both the numerator and denominator are positive, f(x)>0.◻
Question 5. (E) Show that 2x−1(x−1)(2x−3) can be written in the form Ax−1+B2x−3, where A and B are constants to be found. [3 marks](Relevant section: P2 §1.3 Partial fractions.)
(Edexcel 2017 Specifications, P2 Review exercise 1 Q5.)
Solution.
Question 6. (E) Given that 3x+7(x+1)(x+2)(x+3)≡Px+1+Qx+2+Rx+3, where P,Q and R are constants, find the values of P,Q and R. [4 marks](Relevant section: P2 §1.3 Partial fractions.)
(Edexcel 2017 Specifications, P2 Review exercise 1 Q6.)
Solution.
Question 7. (E) f(x)=2(2−x)(1+x)2,x≠−1,x≠2. Find the values of A,B and C such that f(x)=A2−x+B1+x+C(1+x)2 [4 marks](Relevant section: P2 §1.4 Repeated factors.)
(Edexcel 2017 Specifications, P2 Review exercise 1 Q7.)
Solution.
Question 8. 14x2+13x+2(x+1)(2x+1)2≡Ax+1+B2x+1+C(2x+1)2. Find the values of the constants A,B and C.(Relevant section: P2 §1.4 Repeated factors.)
(Edexcel 2017 Specifications, P2 Review exercise 1 Q8.)
Solution.
Question 9. (E) Given that 3x2+6x−2x2+4≡d+ex+fx2+4, find the values of d,e and f. [4 marks](Relevant section: P2 §1.5 Algebraic division.)
(Edexcel 2017 Specifications, P2 Review exercise 1 Q9.)
Solution.
3x2+6x−2≡3(x2+4)−12+6x−2≡3(x2+4)+6x−14⇔3x2+6x−2x2+4≡3+6x−14x2+4
Thus, d=3,e=6,f=−14✓
Question 10. (E) p(x)=9−3x−12x2(1−x)(1+2x). Show that p(x) can be written in the form A+B1−x+C1+2x, where A,B and C are constants to be found. [3 marks](Relevant sections: P2 §1.3 Partial fractions and §1.5 Algebraic division.)
(Edexcel 2017 Specifications, P2 Review exercise 1 Q10.)
Solution.
(i) Step 1: Algebraic division.
The denominator reads:(1−x)(1+2x)=1+x−2x2 and, by algebraic division, we find: 9−3x−12x2=6(−2x2+x+1)−6x−6+9−3x=6(1+x−2x2)−9x+3⇔9−3x−12x21+x−2x2≡6+−9x+31+x−2x2⇔9−3x−12x2(1−x)(1+2x)≡6+−9x+3(1−x)(1+2x)
(ii) Step 2: Partial fractions.
Let −9x+3(1−x)(1+2x)≡B1−x+C1+2x≡B(1+2x)+C(1−x)(1−x)(1+2x) Compare the numerators on both sides: B(1+2x)+C(1−x)≡−9x+3 By the method of substitution: (i)x=1⇒3B=−9+3=−6⇒B=−2(ii)x=−12⇒32C=92+3=152⇒C=5 and we obtain: ⇒−9x+3(1−x)(1+2x)≡−21−x+51+2x
Finally, we find: ⇒9−3x−12x2(1−x)(1+2x)≡6+−9x+3(1−x)(1+2x)≡6−21−x+51+2x✓ and thus: A=6B=−2C=5
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