Question

What is the 2nd term in expansion of `(3u-1)^3`?

Answer 1

`-27u^2`

Explanation:

`(3u-1)^3 = 1*((3u)^3*(-1)^0) + 3*((3u)^2*(-1)^1) + 3*((3u)^1*(-1)^2) + 1*((3u)^0*(-1)^3).`
If you look closely, the sum of powers in each term on the right hand side of the equation above is 3.
Now, the 2nd term:
`-3*9u^2*1 = -27u^2.`