Problem solved ...
First of all, note my error in the last line
(12C7) * (a)^5 * (-b)^7 + (12C7) * (a)^4 * (-b)^8 = 0
Should be:
(12C7) * (a)^5 * (-b)^7 + (12C8) * (a)^4 * (-b)^8 = 0
The negative b on the (-b)^7 comes out the front as it is an odd power ... The other negative...
Homework Statement
I'm asked to find (a/b) in the simplest form if the co-efficient of x^8 is zero in the expansion of:
(1 + x)(a - bx)^12
Homework Equations
Binomial expansion formula ... (a + b)^n = Sum of r --> n (r = 0) (nCr)(a^(n-r) * b^r
The Attempt at a Solution...