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4a^2-9b^2=(2a+3b)(2a-3b)=12
所以该式代入-2a+3b=3，有漏颤坦：洞轮
2a+3b=-4
所以再和返桐-2a+3b=3联立，很容易解得a=-7/4，b=-1/6
12=4a^2-9b^2=(-2a+3b)(-2a-3b)
所以-2a-3b=4
a=-7/4
b=-1/6
4a^2-9b^2=12
(2a+3b)(2a-3b)=12
-2a+3b=3
则键数2a-3b=-3
2a+3b=-4
则好并
4a=-7
a=-7/稿袜首4
b=-1/6
（2a+3b)(2a-3b)=12
-(2a-3b)=3
=>2a+3b=12/(-3)=-4
=>2a+3b=-4
-2a+3b=3
=>6b=-1
=>段察b=-1/纤贺6
=>毁燃派a=-7/4