谁会做？对数计算

1。
(lg5)^2＋(lg2)^2＋lg2×lg25
= (lg5)^2＋(lg2)^2 ＋ 2×lg2 ×lg5
= (lg2 ＋ lg5)^2
= (lg2*5)^2
= 1
选D
2。
9^(log3 3^1/2-log3 5) = 3^2(log3 3^1/2-log3 5)
= 3^2(log3 3^(1/2)/5)
= 3log3 (3^(1/2)/5)^2
= 3^log3 3/25 = 3/25 选A
3。
2lg(x-2y)=lgx+lgy=lg(xy)
得到(x-2y)^2=xy
有x^2-5xy+4y^2=0
得到x/y=4或者x/y＝1
但是x-2y>0并且x>0,y>0
所以x>2y，所以x/y>2
所以答案B

lg平方 5+lg2(lg2+lg25)
=(lg5)^2+(lg2)^2+2*lg5*lg2
=(lg5+lg2)^2
=(lg10)^2
=1
选D

9^(1/2-log3 5)
=(3^2)^(1/2-log3 5)
=3^(1-log3 25)
=3/3^(log3 25)
=3/25
选A

2lg(x-2y)=lgx+lgy
(x-2y)^2=xy
x^2-4xy+4y^2=xy
x^2-5xy+4y^2=0
(x-y)(x-4y)=0
x/y=1或4
log2(x/y)=0或2
x-2y>0,x>0,y>0,x=y舍
log2(x/y)=2
选B

(lg5)^2+lg2*(lg2+lg25)=(lg5)^2+(lg2)^2+(lg2)*(