不解方程:2x+y=7/2005,x+3y=2005/8,试求代数式6x^2+21xy+9y^2的值.

问题描述:

不解方程:2x+y=7/2005,x+3y=2005/8,试求代数式6x^2+21xy+9y^2的值.

3(2X+Y)(X+3Y)=6x^2+21xy+9y^2=3×7/2005×2005/8=21/8