(lg2)^2+lg5lg20-1主要是lg5lg20的化简.(lg2)^2+(1-lg2)(1+lg2)-1这怎么化出来的?
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![(lg2)^2+lg5lg20-1主要是lg5lg20的化简.(lg2)^2+(1-lg2)(1+lg2)-1这怎么化出来的?](/uploads/image/z/5435836-52-6.jpg?t=%28lg2%29%5E2%2Blg5lg20-1%E4%B8%BB%E8%A6%81%E6%98%AFlg5lg20%E7%9A%84%E5%8C%96%E7%AE%80.%28lg2%29%5E2%2B%281-lg2%29%281%2Blg2%29-1%E8%BF%99%E6%80%8E%E4%B9%88%E5%8C%96%E5%87%BA%E6%9D%A5%E7%9A%84%EF%BC%9F)
(lg2)^2+lg5lg20-1主要是lg5lg20的化简.(lg2)^2+(1-lg2)(1+lg2)-1这怎么化出来的?
(lg2)^2+lg5lg20-1
主要是lg5lg20的化简.
(lg2)^2+(1-lg2)(1+lg2)-1这怎么化出来的?
(lg2)^2+lg5lg20-1主要是lg5lg20的化简.(lg2)^2+(1-lg2)(1+lg2)-1这怎么化出来的?
lg5=lg10-lg2=1-lg2
lg20=lg10+lg2
∴(lg2)^2+lg5lg20-1
=(lg2)^2+(1-lg2)(1+lg2)-1
=(lg2)^2+1-(lg2)^2-1
=0