Find the first four nonzero terms in a power series expansion about x_0=4x_0=4  for the differential equation given below. \left(x^2-8x\right)y''+3y=0\left(x^2-8x\right)y''+3y=0.   y\left(x\right)=a_0\left[a+b\left(x-4\right)^2+...\right]+a_1\left[c\left(x-4\right)+d\left(x-4\right)^3+...\right]y\left(x\right)=a_0\left[a+b\left(x-4\right)^2+...\right]+a_1\left[c\left(x-4\right)+d\left(x-4\right)^3+...\right]   a=a= [Fill in the blank], b=b= [Fill in the blank], c=c= [Fill in the blank], d=d= [Fill in the blank], (enter integers or fractions) 多项填空题