已知3x^2-2y=7则9x^2-6y-3的值是
问题描述：
已知3x^2-2y=7则9x^2-6y-3的值是
答
18
答
9x^2-6y-3
=3(3x^2-2y)-3
=3X7-3
=21-3
=18