Date | November 2020 | Marks available | 2 | Reference code | 20N.1.SL.TZ0.T_13 |
Level | Standard Level | Paper | Paper 1 (with calculator from previous syllabus) | Time zone | Time zone 0 |
Command term | Find | Question number | T_13 | Adapted from | N/A |
Question
Consider the graph of the function f(x)=x2-kx.
The equation of the tangent to the graph of y=f(x) at x=-2 is 2y=4-5x.
Write down f′(x).
Write down the gradient of this tangent.
Find the value of k.
Markscheme
* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure. It appeared in a paper that permitted the use of a calculator, and so might not be suitable for all forms of practice.
2x+kx2 (A1)(A1)(A1) (C3)
Note: Award (A1) for 2x, (A1) for +k, and (A1) for x-2 or 1x2.
Award at most (A1)(A1)(A0) if additional terms are seen.
[3 marks]
-2.5 (-52) (A1) (C1)
[1 mark]
-2.5=2×(-2)+k(-2)2 (M1)
Note: Award (M1) for equating their gradient from part (b) to their substituted derivative from part (a).
(k=) 6 (A1)(ft) (C2)
Note: Follow through from parts (a) and (b).
[2 marks]