If y 1 - 2x 2 find the value of dy dx at x -1 - JAMB Mathematics 2005 Question
If y = (1 - 2x)2, find the value of dy/dx at x = -1
A
57
B
27
C
-6
D
-54
correct option: d
y = (1 - 2x)3
let u = 1-2x
du/dx = -2
∴y = u3
dy/du = 3u2
But dy/dx = du/dx * dy/du
= -2 * 3u2
= -6u2
= -6(1-2x)2
At x = -1: dy/dx = -6(1 - 2(-1))2
dy/dx = -6(1 + 2)2
= -6 * 32
= -6 * 9
= -54
let u = 1-2x
du/dx = -2
∴y = u3
dy/du = 3u2
But dy/dx = du/dx * dy/du
= -2 * 3u2
= -6u2
= -6(1-2x)2
At x = -1: dy/dx = -6(1 - 2(-1))2
dy/dx = -6(1 + 2)2
= -6 * 32
= -6 * 9
= -54
Please share this, thanks:
Add your answer
No responses