Which is a related addition fact for 15-6 9

1. a right triangle is graphed on a coordinate plane. find the length of the hypotenuse. round your answer to the nearest tenth. 2. use the angle relationship in the figure below to solve for the value of x. assume that lines a and b are parallel and line c is a transversal.

How to do this , and can some one explain

Find the condition that the zeros of the polynomial f(x) = x^3+3px^2+3px+r may be in a.p.