以知x^2+2xy=3,y^2=2,则代数式3x^2+6xy+y^2的值是

问题描述:

以知x^2+2xy=3,y^2=2,则代数式3x^2+6xy+y^2的值是
A.7B.9C.11D.13

选C
3x^2+6xy+y^2
=3(x^2+2xy)+y^2
=3*3+2
=9+2
=11