(lg2)²+(lg5)²+lg2xlg5=?(lg2)²+(lg5)²+lg2xlg5=?麻烦您把步骤也写上

(lg2)²+(lg5)²+lg2xlg5=?
(lg2)²+(lg5)²+lg2xlg5=?麻烦您把步骤也写上

(lg2)²+(lg5)²+2 lg2xlg5 加了一个2
=(lg2)²+(1-lg2)²+2lg2x(1-lg2)
=lg²2+1-2lg2+lg²2+2lg2-2lg²2
=1

其中lg5=lg(10/2)=lg10-lg2=1-lg2