Date | May 2018 | Marks available | 3 | Reference code | 18M.2.SL.TZ1.T_4 |
Level | Standard Level | Paper | Paper 2 | Time zone | Time zone 1 |
Command term | Find | Question number | T_4 | Adapted from | N/A |
Question
Consider the function , where x > 0 and k is a constant.
The graph of the function passes through the point with coordinates (4 , 2).
P is the minimum point of the graph of f (x).
Find the value of k.
Using your value of k , find f ′(x).
Use your answer to part (b) to show that the minimum value of f(x) is −22 .
Sketch the graph of y = f (x) for 0 < x ≤ 6 and −30 ≤ y ≤ 60.
Clearly indicate the minimum point P and the x-intercepts on your graph.
Markscheme
* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.
(M1)
Note: Award (M1) for correct substitution of x = 4 and y = 2 into the function.
k = 3 (A1) (G2)
[2 marks]
(A1)(A1)(A1)(ft) (G3)
Note: Award (A1) for −48 , (A1) for x−2, (A1)(ft) for their 6x. Follow through from part (a). Award at most (A1)(A1)(A0) if additional terms are seen.
[3 marks]
(M1)
Note: Award (M1) for equating their part (b) to zero.
x = 2 (A1)(ft)
Note: Follow through from part (b). Award (M1)(A1) for seen.
Award (M0)(A0) for x = 2 seen either from a graphical method or without working.
(M1)
Note: Award (M1) for substituting their 2 into their function, but only if the final answer is −22. Substitution of the known result invalidates the process; award (M0)(A0)(M0).
−22 (AG)
[3 marks]
(A1)(A1)(ft)(A1)(ft)(A1)(ft)
Note: Award (A1) for correct window. Axes must be labelled.
(A1)(ft) for a smooth curve with correct shape and zeros in approximately correct positions relative to each other.
(A1)(ft) for point P indicated in approximately the correct position. Follow through from their x-coordinate in part (c). (A1)(ft) for two x-intercepts identified on the graph and curve reflecting asymptotic properties.
[4 marks]