Can someone me figure out how to do this?

What is 10+10+20 about the origin the square root of a triangle.

Let f(x) = 1/x^2 (a) use the definition of the derivatve to find f'(x). (b) find the equation of the tangent line at x=2

If f(x)= x^2 - 4 and g(x)=x^2 + 2 x, (b). (f-g)(x) i think i know the 1st 2 steps: f(x)-g(x) x^2-4 - x^2+2x