this is system of equations
2x + 5y = -1 times this one by 5 to make the y's opposite
-10x -25y = 5
10x - 25y = -5 (this is it times by 5, now add them)
__________
0 + 0 = 0
now since everything cancels and both sides are equal it has infinite solutions beaus they are actually the same line.