differential equations

1- Find two linearly independent solutions of 2x^(2)y''-xy'+(6x+1)y=0, x>0

of the form 

where r1>r2 

y1= x^(r1)*(1+a1x+a2x^2+a3x^3+...)

y2= x^(r2)*(1+ b1x+b2x^2+b3x^3+...)

r1=??

a1=??

a2=??

a3=??

r2=??

b1=??

b2=??

b3=??

2- y''+4xy'-16y=0 y(0)=7 and y'(0)=0

y=??

3- Find the solution of 

4x^(2)y''+3x^(2)y'+y=0, x>0

y1=x^(r)(1+c1x+c2x^(2)+c3x^(3)+....)

r= ??

c1=??

c2=??

c3=??