a) Assuming that you have evaluated \(\displaystyle \lim_{h \to 0}\frac{f(x+h)-f(x)}{h}\) and haven't simply used the rule, then you are correct.

b) A secant is a line that cuts through a curve in two or more points. So in other words, work out the equation of the line between \(\displaystyle A(1, 3)\) and \(\displaystyle B(3,11)\).

c) You know point \(\displaystyle A(1,3)\) lies on the tangent line. So you can substitute \(\displaystyle (x,y) = (1,3)\) into \(\displaystyle y = mx+ c\). You can also evaluate \(\displaystyle m\), since the derivative tells you the gradient of the tangent line at any point (so evaluate it at \(\displaystyle x = 1\)). Then you can solve for \(\displaystyle c\).