Question

(3x+y)二次方-3(3x-y)(x+y)-(x-2y)(x+3y)要过程!

Answer 1

x二次方+y二次方-4x+6y+13=0

(x-2)²+(y+3)²=0

则有：

x-2=0

y+3=0

解得：x=2；y=-3

(3x+y)²-3(3x-y)(x+y)-(x-3y)(x+2y)

=9x²+6xy+y²-3(3x²+2xy-y²)-(x²-xy-6y²)

=9x²+6xy+y²-9x²-6xy+3y²-x²+xy+6y²

=-x²+xy+10y²

=-4-6+90

=80