(√х+√ху)²=x+xy+2√x√xy=x+xy+2x√y
(4√5-7√5)²=16*5+49*5-2*4√5*7√5=80+245-280=45
а)1+81у^2-18y = (9у-1)^2 = (1-9y)^2
f(1\2a+2)= 6(1\2a+2)^2=6(1\4a^2+2a=4)=1,5a^2+12a+24;