I find it of tremendous use to convert to the slope intercept form to easily visualize the lines. The first is: y = 5x - 7 [Dividing both sides by 2] and the second is: -y = -5x + 7 [Subtracting 5x from each side] y = 5x - 7 [Dividing each side by -1]
These two equations represent the same line. If the lines were parallel, there would be no solution. If the lines intersected, there would be only one unique solution satisfying both equations (the point of intersection).
In this case, where the two equations represent the same line, the number of solutions is infinite.
Complement of a Set If U is a universal set and A is a subset of U, then the set of all elements in U that are not in A is called the complement of A and is denoted Ac.
