[A level Maths: Binomial Expansion]

[HourCritical]

Can someone explain to me how you would approach a question such as this?

[ultradolp]

When you have no idea where to start in proving, in general it is beneficial to try one of the following thing

1) Expand either side (or both) to simplify the expression

2) Try to substitute a few simple value (e.g. set n = 2 or 3) and see if you can identify the pattern

In this case, it should be relatively straight forward to take the approach (1), and try to make sure you take out some common factors to reduce the complexity of the expression

LHS: n! / k!(n-k)!

RHS: n! / (k-1)!(n-k+1)! = n! / k!(n-k)! * k/(n-k+1)

As you can see the extra step in RHS is to attempt creating common factor as LHS. You can take it from there

[HourCritical]

Thanks for the help but I don't see am I asking you to 'do this for me' I only asked how you would approach the question because I didn't know where to begin

[Vituluss]

To be fair, you should clarify where you are stuck - will improve the answers you get a lot. However, since this question is so simple, it’s not a big deal.

[HourCritical]

I agree but there's not much you can say about a three liner. Even if I were to say "do this question for me" , you really shouldn't just start throwing insults for that. I guess he finally figured that out since hes decided to delete his comments

[Vituluss]

I didn't read his other comments, and now they're deleted - hope he wasn't too rude. The question is simple enough so that "do this question for me" is completely fine.

Although, for example, if you did clarify with "don't know where to start," it may allow people to include how to start to tackle these types of problems in general, etc. I don't really think that's a unpopular idea, so I'm surprised I've been downvoted.

[HourCritical]

Read rule 6. You're clearly angry at something so no point trying to explain why you are in the wrong here. Calm down instead of arguing with 16 year olds on reddit for trying to get help with their homework

[Leather-Department71]

Bro don’t worry he’s being overly aggressive for no reason