Question
Question: Function f(x) = x<sup>3</sup> + 6x<sup>2</sup> + (9 + 2k) x + 1 is increasing function if...
Function f(x) = x3 + 6x2 + (9 + 2k) x + 1 is increasing function if
A
k ³ 3/2
B
k > 3/2
C
k < 3/2
D
k £ 3/2
Answer
k ³ 3/2
Explanation
Solution
f ¢ (x) = 3x2 + 12x + (9 + 2k) ³ 0
Ž 144 – 4 × 3 × (9 + 2k) £ 0
Ž 12 – 9 – 2k £ 0
Ž k ³ 3/2