Не впевнена чи правильно написала 5 і 6
2х*(2х+3y)-(х+y)^2 = 4х^2+6ху-(х^2+2xy+y^2) = 4x^2+6xy-x^2-2xy-y^2 = 3x^2+4xy-y^2
log2(3)=a log4(9)=log2^2(3^2)=1/2log2(3^2)=1/2*2log2(3)=a
log8(18)= log2^3(2*3^2)=1/3(log2(2)+2log2(3)=1/3(1+a)
log4(81)=1/2log2(3)^4=4*1/2log2(3)=2a
log8(54)=1/3log2(2*27)=1/3((log2(2)+log2(3^3))=1/3(1+3a)