Test Index

JAMB Mathematics 2010 Paper

© africaexams.com

Question : 16

Total: 49

If y = (2x + 1)3 find dy/dx

3(2x+1)²
6(2x+1)
3(2x+1)
6(2x+1)²

Solution:

Concept:

Use the chain rule to differentiate a power of a linear expression.

Explanation:

Given

y = (2x + 1)^3

.

Let

u = 2x + 1

, so

y = u^3

.

Then

\frac{dy}{du} = 3u^2

and

\frac{du}{dx} = 2

.

By the chain rule,

\frac{dy}{dx} = \frac{dy}{du} \cdot \frac{du}{dx}

.

So

\frac{dy}{dx} = 3(2x + 1)^2 \times 2

.

Simplify:

\frac{dy}{dx} = 6(2x + 1)^2

.

Answer:

D.

6(2x+1)^2

© africaexams.com

Go to Question:

Prev Question

Next Question