Date | May Example questions | Marks available | 6 | Reference code | EXM.1.AHL.TZ0.3 |
Level | Additional Higher Level | Paper | Paper 1 (without calculator) | Time zone | Time zone 0 |
Command term | Express | Question number | 3 | Adapted from | N/A |
Question
Let f(x)=4x−5x2−3x+2 x≠1,x≠2.
Express f(x) in partial fractions.
[6]
a.
Use part (a) to show that f(x) is always decreasing.
[3]
b.
Use part (a) to find the exact value of 0∫−1f(x)dx, giving the answer in the form lnq, q∈Q.
[4]
c.
Markscheme
f(x)=4x−5(x−1)(x−2)≡Ax−1+Bx−2 M1A1
⇒4x−5≡A(x−2)+B(x−1) M1A1
x=1⇒A=1 x=2⇒B=3 A1A1
f(x)=1x−1+3x−2
[6 marks]
a.
f′(x)=−(x−1)−2−3(x−2)−2 M1A1
This is always negative so function is always decreasing. R1AG
[3 marks]
b.
0∫−11x−1+3x−2 dx=[ln|x−1|+3ln|x−2|]0−1 M1A1
=(3ln2)−(ln2+3ln3)=2ln2−3ln3=ln427 A1A1
[4 marks]
c.
Examiners report
[N/A]
a.
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b.
[N/A]
c.