[(x+2y)(x-2y)-(x-4y)²]÷4y,其中x=-7,y=0.2求解急._数学解答

[(x+2y)(x-2y)-(x-4y)²]÷4y,其中x=-7,y=0.2
求解急.

人气：131 ℃　时间：2020-09-15 14:17:54

解答

[(x+2y)(x-2y)-(x-4y)^2]÷4y
=(x^2-4y^2-x^2+8xy-16y^2)÷4y
=-5y+2x
代入x=-7 y=0.2
原式=-15