(-2)*x=2分之7
(-2)*(-2)-(-2)*x=7/2
4+2x=7/2 2x=-1/2 x=-1/4
(-2)*x=7/2(-2)²-(-2)x=7/2 4+2x=7/2 2x=7/2-4 2x=-1/2 x=-1/4