因为(2/3a-4)^2=(3/4a+7)^2,
所以
1.(2/3a-4)=(3/4a+7)
8a-48=9a+84
a=-132
2.(2/3a-4)=-(3/4a+7)
8a-48=-9a-84
17a=84-48
17a=36
a=36/17