EduFarming
Your list · 0हिं

Type at least two letters. Press Esc to close.

↑↓ navigate↵ openTAB cycle filter

Increasing & Decreasing Functions · Question 37 of 74

Question 37

MediumOriginal question

Find the interval(s) on which f(x)=2x3+3x2−36x+10f(x) = 2 x^{3} + 3 x^{2} - 36 x + 10 is strictly increasing.

Options for question 37

Show the answer and explanation
CorrectNot quiteAnswer B

Correct answer: B

Explanation

  1. f′(x)=6x2+6x−36=6(x−2)(x+3)f'(x) = 6 x^{2} + 6 x - 36 = 6 \left(x - 2\right) \left(x + 3\right), which is 0 at x=−3x = -3 and x=2x = 2.

  2. f′(x)>0f'(x) > 0 on (−∞,−3)∪(2,∞)(-\infty, -3) \cup (2, \infty) and f′(x)<0f'(x) < 0 on (−3,2)(-3, 2).

  3. So ff is strictly increasing on (−∞,−3)∪(2,∞)(-\infty, -3) \cup (2, \infty).

Worth noting

(−3,2)(-3, 2) is where it is strictly decreasing: the sign of f′f' was read the wrong way.

Concept
Intervals where a function rises or falls
Typical time
90 s
Your time
—
The rule this testsFinding the intervals
Practise this chapter →

Ten questions from Increasing & Decreasing Functions, at your own pace.

Practise this chapter →

Ten questions from Increasing & Decreasing Functions, at your own pace.