Write the equation in vertex form. Then identify the vertex, axis of symmetry, and direction of opening. y = 2x^2 + 2

Evaluate the expression for the given value of the variable 2×(c2-5) for c=4

How to do this , and can some one explain

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.