What number should be added to the expression x^2 + 2x to change it into a perfect square trinomial?

The number of pages in the u. s. tax code exceeds the number of pages in the king james bible by 18,528. the combined number of pages in the tax code and the bible is 21,472

Solve the system of equations. y= 2x y= x^2 - 15

Which of the following lines does not intersect the line y=-2x+3 ? a) y=2x b) y=2x-3 c) y=2x+3 d) y=-2x-3