Please help me solve this!!

If a || b and b | y, then ? a) x || y. b) x | a. c) a | y. d) a || y.

Parabolas y=−2x^2 and y=2x^2+k intersect at points a and b that are in the third and the fourth quadrants respectively. find k if length of the segment ab is 5.

Solve the equation for b: a= (1/2)(b)(h)