Question

(-x的2次方+3xy-2分之一y的2次方)-(-2分之一x的2次方+4xy-2分之三y的2次方)=

快点嘛答案

Answer 1

(-x^2 + 3xy + 1/2 y^2 ) - ( - 1/2x^2 + 4xy - 3/2 y^2)
= - x^2 + 3xy + 1/2 y^2 + 1/2 x^2 - 4xy + 3/2 y^2
= ( - x^2 + 1/2x^2) + ( 3xy - 4xy ) + ( 1/2 y^2 + 3/2 y^2)
= -1/2 x^2 - xy + 2y^2

追问

答案括号中缺一

追答

= - 1/2 x^2 - (xy + y^2) + y^2