# Thread: tangent of a curve

1. ## tangent of a curve

A curve has the equation y=2x^2-6x+c, where c is a constant.

Find the value of c for which the line y+2x=8 is a tangent to the curve

2. Rewrite your tangent as $y = -2x + 8$.

The gradient of this tangent is $-2$.

So this means $\frac{dy}{dx} = -2$.

Find the derivative, set it equal to $-2$ and solve for $c$.