-x+2y = 2 x-2y = -2 Solve the second one for x x-2y = -2 x = -2+2y Substitute (-2+2y) for x in the first one: x-2y = -2 (-2+2y)-2y = -2 -2+2y-2y = -2 -2 = -2 This equation -2 = -2 is an identity. When trying to solve using substitution or elimination, if we get an identity, that means there are infinitely many solutions. The graphs are the same line. Answer: There are infinitely many solutions. This is called a DEPENDENT SYSTEM. ------------------------------------------------------------------ ------------------------------------------------------------------ [Note: BTW, in other problems when trying to solve using substitution or elimination, if we get a contradiction, such as -2 = -1, that means there are NO solutions. The graphs are parallel lines. That would be called an INCONSISTENT SYSTEM.] Edwin