(25 points) Find two linearly independent solutions of y"' + 9xy = 0 of the form y1 = 1+ a3x^3 + a6x^6 + ...
y2 = x + b4x^4 + b7x^7 + .. Enter the first few coefficients: a3 = ___
a6 = ___
b4 = ___
b7 = ___