In order to solve this you have to remember the formlua for the perfect quadratic trinomial:
IN the example you have A^2 and 2ab, since A=1, then the 2x will resulto from the multiplication of b and a multiplied by 2, so we just have to divide 2x by 2x to get b:
The intersection of the two lines is the solution to the system of linear equations. The two lines intersect at (-2.5, -2), then the solution to the system is x = -2.5 and y = -2