Thread: Gradient of normal

Find the equation of the normal to the curve y = 4x² - 7x + 2 at the point (2, 4).

Is this right?

dy / dx = 8x - 7

x-co-ordinate = 2
16 - 7 = 9 [tangent]
normal] = -1/9.

y-4 / x-2 = -1/9

9y - 36 = -x + 2
9y + x + 38 = 0

Dear db5vry,

The start is perfect, the sprint is excellent, but in the last step you slid on a banane heel.

Is it -34, or -38, rather than +38?

9y - 36 = -x + 2 --> 9y+x = 38 --> 9y + x - 38 = 0