00:01
All right, in this video, they asked for how can factoring make numbers 21, 22, and 67 easier.
00:07
And i'm going to use a particular one and kind of show you how to do this.
00:10
So all of these right here, they have a relationship or something in common, is there all some of cubes, or at least in the numerator anyway? so we can use a factoring technique to kind of make the, i guess, essentially, the functioner sequence a lot smaller.
00:29
So we actually plug in numbers.
00:30
It's not so much, it's not so time -consuming.
00:32
So i'm going to work on, i'm sure you how to do this with the number 67, but it does work for the other two.
00:38
Okay, so the first you want to do is see what's actually being cubed.
00:41
So again, i'm just going to kind of focus on this right here for right now.
00:45
So the way i can rewrite this is that, again, each part, or at least the numer is being cubed.
00:50
So i can obviously x, subscript i is being cubed, but also can rewrite 1 ,000 as 10 cubed.
00:57
Okay? so what i can do now is use a factoring technique to break that down and then kind of show you how you can.
01:03
Make this function or sequence a little bit smaller or series smaller.
01:07
So the technique i use for factoring sum of cubes is the kind of notation here.
01:14
I call it sum us.
01:16
Okay, s stands for square.
01:20
O stands for opposite, m stands for multiply, a stands for add, oops, and the s also stands for square again.
01:32
Okay, and what this does, it helps you break down the trinole that you're bunch you're going to get.
01:37
So what's going to happen is you're going to break this into a binomial, a two -term expression times a trinomial, and this will help you with the trinomial.
01:45
Okay, but you need the binomial first.
01:47
Okay, so for the binomial, what you're doing, you're basically just take off the cube part to our expression we have right above it.
01:53
So we're going to do s, subscript i plus 10...