Date | November 2015 | Marks available | 2 | Reference code | 15N.1.hl.TZ0.10 |
Level | HL only | Paper | 1 | Time zone | TZ0 |
Command term | Find | Question number | 10 | Adapted from | N/A |
Question
A given polynomial function is defined as f(x)=a0+a1x+a2x2+…+anxn. The roots of the polynomial equation f(x)=0 are consecutive terms of a geometric sequence with a common ratio of 12 and first term 2.
Given that an−1=−63 and an=16 find
the degree of the polynomial;
the value of a0.
Markscheme
the sum of the roots of the polynomial =6316 (A1)
2(1−(12)n1−12)=6316 M1A1
Note: The formula for the sum of a geometric sequence must be equated to a value for the M1 to be awarded.
1−(12)n=6364⇒(12)n=164
n=6 A1
[4 marks]
a0an=2×1×12×14×18×116, (an=16) M1
a0=16×2×1×12×14×18×116
a0=2−5(=132) A1
[2 marks]
Total [6 marks]