4a^2-9b^2=12且-2a+3b=3求a和b急!

来源:学生作业帮助网 编辑:作业帮 时间:2024/05/05 06:25:45

4a^2-9b^2=12且-2a+3b=3求a和b急!
4a^2-9b^2=12且-2a+3b=3求a和b急!

4a^2-9b^2=12且-2a+3b=3求a和b急!
12=4a^2-9b^2=(-2a+3b)(-2a-3b)
所以-2a-3b=4
a=-7/4
b=-1/6

4a^2-9b^2=(2a+3b)(2a-3b)=12
所以该式代入-2a+3b=3,有:
2a+3b=-4
所以再和-2a+3b=3联立,很容易解得a=-7/4,b=-1/6

4a^2-9b^2=12
(2a+3b)(2a-3b)=12
-2a+3b=3
则2a-3b=-3
2a+3b=-4

4a=-7
a=-7/4
b=-1/6

(2a+3b)(2a-3b)=12
-(2a-3b)=3
=>2a+3b=12/(-3)=-4
=>2a+3b=-4
-2a+3b=3
=>6b=-1
=>b=-1/6
=>a=-7/4