Here's the question you clicked on:
Mubi
A curve has equation y= x^3+ 3x^2 -9x+k, where k is a constant. 1/ write down an expression for dy/dx 2/ find the x-coordinates of the two stationary points on the curve. 3/ hence find the two values of k for which the curve has stationary point on the x-axis.
I'm sure you know the power rule for derivatives. Right? So is there something specific about the problem that's perhaps troubling you?
Is the answer for no 1/ (1/4)x^4+x^3-(9/2)x^2+k