How do I set out my working properly for (binomial): (1 Viewer)

[planino]

Find the coefficient of a3 in the expansion of (3 − 4a)(a − 3)^4

Can we just write out the general term for (a-3)^4 and multiply by (3-4a), and collect like terms?

 

[planino]

I got -252, but only after fully expanding (a-3)^4 and then multiplying the terms in a^2 by (-4a) and the term in a^3 by 3, and then added them.

I hope there's a faster way than this.

 

[Carrotsticks]

I got -252, but only after fully expanding (a-3)^4 and then multiplying the terms in a^2 by (-4a) and the term in a^3 by 3, and then added them.

I hope there's a faster way than this.

That's the way to go. When you master it, you can do such questions in about 10 seconds.

 

[planino]

Haha that was actually encouraging, considering I was feeling like shit after forgetting a "+C" when I integrated (and after 2U as well).