Cos57° = cos (45° + 12°)
f (x0 + Δx) = f(x0) + f'(x0)*Δx =
= cos(pi/4) - sin (pi/4)*pi/15 =
= 1/√2 - pi/15√2 ≈ 0,559
В-А=2а²+3а-1-а²+3а-2=а²+6а-3
-а²+3а-2-2а²-3а+1=-3а²-1
А*В=2а^4+3а³-а²-6а³-9а²+3а+4а²+6а-2=2а^4-3а³-6а²+9а-2
(x+8)(7x+5) - (x+8)(5x+7)
_____________________ = 0
(5x+7)(7x+5)
ОДЗ: x не= -1,4 ; -5/7
(x+8)(7x+5) - (x+8)(5x+7)=0
(x+8)(7x+5-5x-7)=0
(x+8)(2x-2)=0
x+8=0 2x-2=0
x= -8 x=1
Ответ : 1