化简求值:已知x、y满足:x2+y2-4x+6y+13=0,求代数式(3x+y)2-3(3x-y)(x+y)-(x-3y)(x+3y)的值.

问题描述:

化简求值:已知x、y满足:x2+y2-4x+6y+13=0,求代数式(3x+y)2-3(3x-y)(x+y)-(x-3y)(x+3y)的值.

原式=9x2+6xy+y2-3(3x2+3xy-xy-y2)-(x2-9y2) =9x2+6xy+y2-9x2-6xy+3y2-x2+9y2       =-x2+13y2           &n...