Free points here u go

For which pairs of functions is (f•g)(x)=12x? f(x)=3-4x and g(x)=16x-3 f(x)=6x2 and g(x)= 2/x f(x)= and g(x) = 144x f(x)=4x and g(x) =3x

Solve for x and select the correct answer

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.