Two linearly independent solutions of the differential equation y" - 6y + 9y = 0 are:____________
a. y_1 = e3x, y_2 = xe3x
b. y_1 = e-3x, y_2 = xe-3x
c. y_1 = e3x, y_2 = xe-3x
d. y_1 =e3x cos(x),
e. y_2 = xe3x sin(x)
f. y_1 = e-3x cos(3)
g. y_2 = e-3x sin(x)