Find the equation of the line satisfying the given conditions, giving it in slope–in...

Find the equation of the line satisfying the given conditions, giving it in slope–intercept form if possible.

Refer to the given figure and complete parts (a)–(h) to prove that if two lines are perpendicular and neither line is parallel to an axis, then the lines have slopes whose product is –1.

(a) In triangle OPQ, angle POQ is a right angle if and only if