Let f(x)=x^2+x+13. What is the value of x for which the tangent line to the graph of y=f(x) is parallel to the x -axis?

Can someone show/help me step by step to solve this? I don't know how to begin working on the problem.

Question

Let f(x)=x^2+x+13. What is the value of x for which the tangent line to the graph of y=f(x) is parallel to the x -axis? 

Can someone show/help me step by step to solve this? I don't know how to begin working on the problem.

anonymous · Answer

take the derivative, set it equal to zero and solve
if you are not using calculus i have no idea how to to it

anonymous · Answer

oooh it is a quadratic
nvm
you don't need calc, find the vertex