A/(a²-ab)-b/(a²-b²)=a/a(a-b) -b/(a-b)(a+b)=1/(a-b) -b/(a-b)(a+b)=(a+b-b)/(a²-b²)=
=a/(a²-b²)
a=√2 b=√5
√2/(4-5)=-√2/3
cos6xcos5x+sin6xsin5x=-1 cos(6x-5x)=-1 cosx=-1 x=pi+2pin
Пожалуйста.............................................................
У=-sin(x+П/2)=-cos x
X=-П/2
-cos(-П/2)=-cos П/2==0
X^4 - 10x^2 + 25 = 0
(x^2 - 5)^2 = 0
x^2 - 5 = 0
x^2 = 5
x = ± √5