X2-3x+9/(х+3)(х2-3х+9) - х2+18/х2+27=х2-3х+9-х2-18/(х+3)х2-3х+9)=-9-3х(х+3)(х2-3х+9)=
=-3(х+3)/(х+3)(х2-3х+9)= 3/х2-3х+9
1) 2cox = √3
cosx = √3/2
x = +- arccos(√3/2) + 2πk, k ∈ Z
x = +- π/6 + 2πk
2)sin x = 1/2
x = (-1)^k arcsin(1/2) + πk, k ∈ Z
x = (-1)^k π/6 + πk
3)cos2x = -1
2x = π + 2πk, k ∈ Z
x = π/2 + πk
B+b+a+a=2b+2a
x-y-z+y=y+y+x-z=2y+x-z
c-10+15-c=c-c10+15=25
x+x-15+15=2x-30
m+m+1+m-20=3m-19
4х+3у-6х+7у+3х-6у=-х+4у=-(-3)+4*5,03=-3+20,12=17,12