The teacher will be very surprised to see your correct solution 😉
2 (x - 9)*(x - a) = x - 4*a*x + b
(x-9)*(x-a) = x^2-4*a*x+b
x-9x-a = x^2-4*a*x+b
(-9 + x)*(x - a) = x^2-4*a*x+b
b = 9 + x^2 - 4*a*x / ((9 - b + (-9 + x)*(x - a))/b)
sum
-9*re(x) + 3*re(a*x) + 9*re(a) + I*(-9*im(x) + 3*im(a*x) + 9*im(a))
=
-9*re(x) + 3*re(a*x) + 9*re(a) + I*(-9*im(x) + 3*im(a*x) + 9*im(a))
product
-9*re(x) + 3*re(a*x) + 9*re(a) + I*(-9*im(x) + 3*im(a*x) + 9*im(a))
=
-9*re(x) + 3*re(a*x) + 9*re(a) + 3*I*(-3*im(x) + 3*im(a) + im(a*x))
-9*re(x) + 3*re(a*x) + 9*re(a) + 3*i*(-3*im(x) + 3*im(a) + im(a*x))
b1 = -9*re(x) + 3*re(a*x) + 9*re(a) + I*(-9*im(x) + 3*im(a*x) + 9*im(a))
b1 = i*(9*im(a) - 9*im(x) + 3*im(a*x)) + 9*re(a) - 9*re(x) + 3*re(a*x)