Mathematics · Oct / Nov 2021 · Paper 42 · Question 10

(2, –10) and (–2, 22) [5]

B2 for 3x2 – 12 isw

or B1 for 3x2 + k or px2 – 12 (p ≠ 0) or for 3x2 – 12 + 6 isw

M1 for setting their derivative = 0 or dy dx = 0

B1 for x = ± 2 or for one correct coordinate pair

(2, –10) minimum with correct reason or sketch (–2, 22) maximum with correct reason or sketch [3]

B2 for 1 correct with correct reasoning or B2FT for correct evaluation with correct 2nd derivative for both of their different x values

or M1 for showing [2nd derivative =] 6x or gradients for one value on either side of one correct stationary point or for reasonable sketch of cubic