先化简再求值:(a+b)^2+(a-b)^2+(-2a+b)(a+2b)其中a=2/3,b=1/2
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/27 17:46:51
![先化简再求值:(a+b)^2+(a-b)^2+(-2a+b)(a+2b)其中a=2/3,b=1/2](/uploads/image/z/1620981-45-1.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%E5%86%8D%E6%B1%82%E5%80%BC%3A%28a%2Bb%29%5E2%2B%28a-b%29%5E2%2B%28-2a%2Bb%29%28a%2B2b%29%E5%85%B6%E4%B8%ADa%3D2%2F3%2Cb%3D1%2F2)
先化简再求值:(a+b)^2+(a-b)^2+(-2a+b)(a+2b)其中a=2/3,b=1/2
先化简再求值:(a+b)^2+(a-b)^2+(-2a+b)(a+2b)其中a=2/3,b=1/2
先化简再求值:(a+b)^2+(a-b)^2+(-2a+b)(a+2b)其中a=2/3,b=1/2
(a+b)^2+(a-b)^2+(-2a+b)(a-2b)
=a^2+2ab+b^2+a^2-2ab+b^2-2a^2-2b^2+5ab
=5ab=5*2/3*1/2=5/3
原式=2a²+2b²-2a²-3ab+2b²
=4b²-3ab
=4×﹙1/2﹚²-3×2/3×1/2
=1-1
=0.