I'm assuming you haven't taken calculus. For #1, you are looking at f(x) which is a parabola. You should know that a parabola that opens up has a minimum point, called the vertex. All other points increase from that point. Use that info to solve the problem.

For #2 think about how do you find slope normally? Think of it as two general points. (a+h, f(a+h)) is one and choose any other general point on f(x) - say (c, f(c)). I don't get why they tell you the first point is the sum of two variables when it's easier to just user one but it's still solvable.