(急!)若x^2与2y^2的和为a,1+3x^2与x^2-y^2的差为b,求a的2倍与b的3倍的差

来源:百度知道 编辑:互助问答吧 时间:2020/07/12 00:55:32
RT,请给出过程,谢谢!

解:x^2 + 2y^2 = a

1+3x^2-(x^2-y^2)=b
1+3x^2-x^2+y^2=b
1+ 2x^2 +y^2 =b

2a-3b=2(x^2+2y^2)-3(1+2x^2+y^2)
=2x^2+4y^2-3-6x^2-3y^2
=-4x^2 + y^2 - 3