Find the general solution to y′′+9y=0y'' + 9y = 0y′′+9y=0.
y=C1cos(3x)+C2sin(3x)y = C_1 \cos(3x) + C_2 \sin(3x)y=C1cos(3x)+C2sin(3x)
y=C1e3x+C2e−3xy = C_1 e^{3x} + C_2 e^{-3x}y=C1e3x+C2e−3x
y=C1cos(9x)+C2sin(9x)y = C_1 \cos(9x) + C_2 \sin(9x)y=C1cos(9x)+C2sin(9x)
y=(C1+C2x)e3xy = (C_1 + C_2 x) e^{3x}y=(C1+C2x)e3x