Tìm x : x^2 - 36=0; x^2 -2x =-1; x^3 + 3x^2=-3x - 1; x^ 3 - 3x^2 + 3x - 1 = 27

Tìm x
a)x^2-36=0
b)x^2 -2x=-1
c)x^3+3x^2=-3x-1
d)x^3-3x^2+3x-1=27