已知4x^2-3y^2=12,3x^2+2y^2=21,求代数式14x^2-2y^2的值._数学解答

已知4x^2-3y^2=12,3x^2+2y^2=21,求代数式14x^2-2y^2的值.

人气：389 ℃　时间：2019-08-18 19:11:35

解答

4x^2-3y^2=12,3x^2+2y^2=21
两式相加,
7x^2-y^2=12+21=33

14x^2-2y^2
=2(7x^2-y^2)
=2*33
=66