Thread: tangents

find an equation of the line tangent to f(x)=x^2-4x at P(3,-3)
thank you

Originally Posted by mxhockey140

find an equation of the line tangent to f(x)=x^2-4x at P(3,-3)
thank you

Hi mxhockey,

The tangent line you are looking for has the form where m is the same as the gradient of your function f(x) at (3, -3). So just find f'(x) and plug in x = 3 to find m.

Well, we seek a line crossing a given point. And tangent means "toucher" that means the slope tangent = local slope of the curve at the given point.
in the end we can calculate the local slope with usage of derivation.