1
log(2)72*log(2)18-log(2)12*log(2)81=
=(3+2log(2)3)*(1+2log(2)3)-4log(2)3*(2+log(2)3)=
=3+6log(2)3+2log(2)3+4log²(2)3-8log(2)3-4log²(2)3=3
3
[(1-log)26)(1+log(2))*1/(1+log(2)6)+log(2)6]*7=
=(1-log(2)6+log(2)6)*7=1*7=7
5
[(1+log(3)5)²+(1+log(3)5)*log(3)5-2log²(3)5]/(1+log(3)5+2log(3)5)=
=(1+2log(3)5+log²(3)5+log(3)5+log²(3)5-2log²(3)5)/(1+3log(3)5)=
=(1+3log(3)5)/(1+3log(3)5)=1
7
log(5)3=a
(1-a³)/(a+1/a+1)*(1-a) -a=(1-a)(1+a+a²)*a/[(a²+1+a)*(1-a)]-a=
=a-a=0