ax+by=2 cx-7y=8甲正确的解出x=3 y=-2
3a-2b=2,3c+14=8
c=-2
把c看错啦,解得x=-2 y=2
-2a+2b=2
a=4,b=5
方程组:4x+5y=2,-2x-7y=8
a=4