(x+2)y'''=y''
y'' = z
(x+2)z'=z
z'/z = 1/(x+2)
∫ z'/z = ∫ 1/(x+2)
ln z = ln (x+2) +ln C
z = C(x+2)
y'' = C(x+2)
∫ y'' =∫ C(x+2)
∫ y'' = C ∫ (x+2)
y' = C (x^2/2+2x) +C1
∫ y' =∫ ( C (1/2*x^2+2x) +C1 )
y = C (1/2*x^3/3+2*x^2/2) +C1*x +C2
y = C*x^2/6 (x+6) +C1*x +C2
C = C/6
y = C*x^2 *(x+6) +C1*x +C2