lg25+2/3lg8+lg5·lg20+lg^22我见到个过程是lg25+2/3lg8+lg5乘以lg20+lg^22=2lg5+2lg2+lg5*(2lg2+lg5)+lg2*lg2=2(lg5+lg2)+(lg5)^2+2lg2*lg5+(lg2)^2=2lg10+(lg5+lg2)^2=2+1^2=3 我想问一下,第3步怎么到第4步的?错了,是第2步怎么到第3
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/29 01:46:14
![lg25+2/3lg8+lg5·lg20+lg^22我见到个过程是lg25+2/3lg8+lg5乘以lg20+lg^22=2lg5+2lg2+lg5*(2lg2+lg5)+lg2*lg2=2(lg5+lg2)+(lg5)^2+2lg2*lg5+(lg2)^2=2lg10+(lg5+lg2)^2=2+1^2=3 我想问一下,第3步怎么到第4步的?错了,是第2步怎么到第3](/uploads/image/z/1326204-36-4.jpg?t=lg25%2B2%2F3lg8%2Blg5%C2%B7lg20%2Blg%5E22%E6%88%91%E8%A7%81%E5%88%B0%E4%B8%AA%E8%BF%87%E7%A8%8B%E6%98%AFlg25%2B2%2F3lg8%2Blg5%E4%B9%98%E4%BB%A5lg20%2Blg%5E22%3D2lg5%2B2lg2%2Blg5%2A%282lg2%2Blg5%29%2Blg2%2Alg2%3D2%28lg5%2Blg2%29%2B%28lg5%29%5E2%2B2lg2%2Alg5%2B%28lg2%29%5E2%3D2lg10%2B%28lg5%2Blg2%29%5E2%3D2%2B1%5E2%3D3+%E6%88%91%E6%83%B3%E9%97%AE%E4%B8%80%E4%B8%8B%2C%E7%AC%AC3%E6%AD%A5%E6%80%8E%E4%B9%88%E5%88%B0%E7%AC%AC4%E6%AD%A5%E7%9A%84%3F%E9%94%99%E4%BA%86%2C%E6%98%AF%E7%AC%AC2%E6%AD%A5%E6%80%8E%E4%B9%88%E5%88%B0%E7%AC%AC3)
lg25+2/3lg8+lg5·lg20+lg^22我见到个过程是lg25+2/3lg8+lg5乘以lg20+lg^22=2lg5+2lg2+lg5*(2lg2+lg5)+lg2*lg2=2(lg5+lg2)+(lg5)^2+2lg2*lg5+(lg2)^2=2lg10+(lg5+lg2)^2=2+1^2=3 我想问一下,第3步怎么到第4步的?错了,是第2步怎么到第3
lg25+2/3lg8+lg5·lg20+lg^22
我见到个过程是
lg25+2/3lg8+lg5乘以lg20+lg^22
=2lg5+2lg2+lg5*(2lg2+lg5)+lg2*lg2
=2(lg5+lg2)+(lg5)^2+2lg2*lg5+(lg2)^2
=2lg10+(lg5+lg2)^2
=2+1^2=3
我想问一下,第3步怎么到第4步的?
错了,是第2步怎么到第3步的
lg25+2/3lg8+lg5·lg20+lg^22我见到个过程是lg25+2/3lg8+lg5乘以lg20+lg^22=2lg5+2lg2+lg5*(2lg2+lg5)+lg2*lg2=2(lg5+lg2)+(lg5)^2+2lg2*lg5+(lg2)^2=2lg10+(lg5+lg2)^2=2+1^2=3 我想问一下,第3步怎么到第4步的?错了,是第2步怎么到第3
你有没有发现在第二步的后面三项(lg5)^2+2lg2*lg5+(lg2)^2
是完全平方,就是a^2+2ab+b^2=(a+b)^2类型的,具体点(lg5)^2+2lg2*lg5+(lg2)^2=(lg5+lg2)^2这是一个等式
至于第二步的第一项利用对数的运算法则就可以得出.
lg25+(2/3)lg8+lg5·lg20+lg^22
=2lg5+2lg2+lg5*(2lg2+lg5)+lg2*lg2
=2*(lg5+lg2)+2*lg5*lg2+(lg5)^2+(lg2)^2
=2*lg(5*2)+(lg5+lg2)^2
=2*lg(10)+(lg(5*2))^2
=2+(lg(10))^2
=2+1
=3