2.
(х-4)² - (х+1)(х-1) = х²-8х+16 - х²+1 = -8х + 17,
при х=5/8:
-8 * 5/8 + 17 = -5 + 17 = 12,
3.
а)
4х² - (х-3у)² = (2х - (х-3у))*(2х + (х-3у)) = (2х-х+3у)(2х+х-3у) =
= (х + 3у)(3х - 3у) = 3*(х + 3у)(х - у),
б)
(2а+7в)² - (3а-5в)² = ((2а+7в) - (3а-5в))*((2а+7в) + (3а-5в)) =
= (2а+7в - 3а+5в)*(2а+7в + 3а-5в) = (12в - а)(2в + 5а),
4.
(2в+в²)² + в²(5-в)(5+в) - 4в(в²-3) =
= 4в²+4в³+в⁴ + 25в²-в⁴ - 4в³ + 12в =
= 29в² + 12в,
5.
а)
(у+4)(у²-4у+16) = у³ + 64,
(к+3)(к-11) + (к+6)² = к²-11к+3к-33 + к²+12к+36 = 2к² + 4к + 3