Find the Fourth term of (6x+5)^5
I always am confused with these because I never know which end I am supposed to start from.
I guess there is some convention that I can never remember.
The coefficients for a power of 5 are 5C0, 5C1, 5C3, 5C4, 5C5 and these are 1,5, 10, 5,1
So, depending on which end you start from, the forth one is either
\(5*(6x)^4*5^1 = 5*6^4x^4*5=25*1296*x^4=32400x^4\\ or\\ 5*5^4*(6x)^1=5^5*6x=18750x\)