先化简再求值:[(x+3y)(x-3y)-(x+3y)^2]÷4y
问题描述:
先化简再求值:[(x+3y)(x-3y)-(x+3y)^2]÷4y
答
[(x+3y)(x-3y)-(x+3y)^2]÷4y
=[(x²-9y²)-(x²+9y²+6xy)]÷4y
=(x²-9y²-x²-9y²-6xy)÷4y
=-6xy÷4y
=-3x/2