校花的贴身高手雨海天:一道数学题 急用
来源:百度文库 编辑:中科新闻网 时间:2024/05/13 15:56:59
计算:
(x+y/2)^2-(x-y/2)^2(要步骤)
(x+y/2)^2-(x-y/2)^2(要步骤)
=(x+y/2+x-y/2)(x+y/2-x+y/2)
=2xy
依据公式为:a^2-b^2=(a+b)×(a-b)
这里是把(x+y/2)当作a,将(x-y/2)当作b
=(x+y/2+x-y/2)(x+y/2-x+y/2)=2x*y
(x+y/2)^2-(x-y/2)^2=(x+y/2+x-y/2)(x+y/2-x-y/2)=xy
平方差公式!
解:(x+y/2)^2-(x-y/2)^2
={(x+y)/2 +(x-y)/2}×{(x+y)/2 -(x-y)/2}
=(2x/2)×(2y/2)=xy