Binomials

If yyou have the expand (1/2x + x/2)^3 should you first make the first bit of the bracket 1??
Because in another example it said you should make it (1+...). When would you have to do this??

Thanks!!

Reply 1

TSR Jessica

Sorry you've not had any responses about this. :frown:

Why not try posting in a specific subject forum- you might have more luck there.

Here's a link to our subject forum which should help get you more responses. :redface:

Reply 2

ManLike007

No you don't because if you look at that other example you mentioned, the bracket is (1+/-....)^... to start off with (1+...)

Let's just say you had to expand (1+3x)^5 ok. You would start off with: 5C0 (1)^5 + 5C1 (1)^4(3x)^1 + 5C2 (1)^3(3x)^2..... OR 5C0 (1)^5 + 5C1 (3x) + 5C2 (3x)^2 + .....
This would be simplified to: 1 + 15x + 90x^2

However in your example of (1/2x + x/2)^3, you would start off with: 3C0 (1/2x)^3 + 3C1 (1/2x)^2(x/2) + .....
Now simplify this and you'd get 1/8x^3 as your first term. That's because the left number in the bracket (I don't know the name of it, sorry) is not 1.

If this is not clear, let me know, writing it on paper may be easier to understand.