Thread: tgnts n norms

The equation of a curve is y = 3x^2 - 2x + 1

find the coordinates of the point R on the curve at which the gradient is -14.

do i put the result of dy/dx to equal -14? doing that will not find me 2 points though..

Originally Posted by x-disturbed-x

The equation of a curve is y = 3x^2 - 2x + 1

find the coordinates of the point R on the curve at which the gradient is -14.

do i put the result of dy/dx to equal -14? doing that will not find me 2 points though..

There is only one point at which the gradient is -14 and yes you do solve:



to find the x-coordinate of the point, then substitute that value back
into the original equation to find the corresponding y.

RonL

i know the gradient and the x coordinate. the original equation before differentiation / simplification was

y = 3x^2 - 2x + 1

how do i find the y coordinate?

Originally Posted by x-disturbed-x

i know the gradient and the x coordinate. the original equation before differentiation / simplification was

y = 3x^2 - 2x + 1

how do i find the y coordinate?

The x-coordinate of the point at which the derivavtive is -14 is
-2.

Since the required point is on the curve , and we
already know the x-coordinate, we need only substitute
this into the equation for y will give the y-coordinate.

RonL

y = 17?

Originally Posted by x-disturbed-x

y = 17?

Yep.

RonL

Thanks for all your help