已知x+3y=12,则(x平方+2xy - 3y平方)除以(x-y)等于多少

问题描述:

已知x+3y=12,则(x平方+2xy - 3y平方)除以(x-y)等于多少

(x平方+2xy - 3y平方)除以(x-y)
=(x-y)(x+3y)/(x-y)
=x+3y
=12