Date | May 2017 | Marks available | 3 | Reference code | 17M.2.SL.TZ1.T_6 |
Level | Standard Level | Paper | Paper 2 | Time zone | Time zone 1 |
Command term | Find | Question number | T_6 | Adapted from | N/A |
Question
Consider the function .
The tangent to the graph of at is parallel to the line .
Find .
Show that .
Find the equation of the tangent to the graph of at . Give your answer in the form .
Use your answer to part (a) and the value of , to find the -coordinates of the stationary points of the graph of .
Find .
Hence justify that is decreasing at .
Find the -coordinate of the local minimum.
Markscheme
* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.
(A1)(A1)(A1)
Note: Award (A1) for , (A1) for and (A1) for . Award at most (A1)(A1)(A0) if additional terms are seen.
[3 marks]
(M1)(M1)
Note: Award (M1) for equating their derivative to 21. Award (M1) for substituting 2 into their derivative. The second (M1) should only be awarded if correct working leads to the final answer of .
Substituting in the known value, , invalidates the process; award (M0)(M0).
(AG)
[2 marks]
(M1)
Note: Award (M1) for substituting 2 into .
(M1)
Note: Award (M1) for correct substitution of 21, 2 and their 7 into gradient intercept form.
OR
(M1)
Note: Award (M1) for correct substitution of 21, 2 and their 7 into gradient point form.
(A1) (G2)
[3 marks]
(or equivalent) (M1)
Note: Award (M1) for equating their part (a) (with substituted) to zero.
(A1)(ft)(A1)(ft)
Note: Follow through from part (a).
[3 marks]
(M1)
Note: Award (M1) for substituting into their derivative, with substituted. Follow through from part (a).
(A1)(ft) (G2)
[2 marks]
(therefore is decreasing when ) (R1)
[1 marks]
(M1)
Note: Award (M1) for correctly substituting 6 and their 1 into .
(A1)(ft) (G2)
Note: Award, at most, (M1)(A0) or (G1) if answer is given as a coordinate pair. Follow through from part (c).
[2 marks]