Ответ:

3.

а)–12х^6у^6

б)8/3х^2у^8*(–3/2ху^3)^4=8/3х^2у^8*81/16х^4у^12=

=27/2х^6у^20

5.

а)–6х+3х^2+3х^2–5х–2=6х^2-11х–2

б)7х+56+х^2–64=х^2+7х–8=(х–1)*(х+8)

в)4х^2+20х–4х^2–20х–25=–25