Again, we'll group like terms, the -u^2 and -3u^2 are like terms.

As well as the 5u and -7u. So, grouping them together gives us

(-u^2-3u^2)+(5u-7u)-6=-4u^2-2u-6, which would be our answer.

And now, if we try to do this vertically, we have to be careful here because of the

subtraction. In other words, we have -u²+5u, and then

minus but it's minus the entire second polynomial, this -(3u²+7u+6).

So, -u^2-3u^2 is -4u^2. And then, 5u-7u is -2u.

Now, we have to be very careful with this constant term here.

So, let's put a +0 here in the first polynomial.

Because when we're subtracting, it's really 0-6 or -6, which is the same

answer. Now often, when we subtract vertically,

you'll see the following instead. We have the -u^2+5u, but then subtraction

means we add the opposite. So, plus and then the opposite of the

second polynomial is -3^2-7u-6. And, so now, we can add, we get

-4u^2-2u-6, which again is the same answer.

So, be careful with subtraction. Alright, let's look at one more example.

[SOUND] Notice now, we have three polynomials.

But we are subtracting the second and adding the third.

So, we need to be careful when we are removing our parentheses.

That is, this is equal to -5w^2-5w+3. And then, minus a -4w^2 or +4w^2, and

then minus a -2w or +2w. And then, minus a -2 or +2.

And then, +3w-2w^2+1. Again, grouping like terms, -5w^2, 4w62,

and -2w62 are like terms. As well as the -5w, 2w, and 3w, as are

the 3, the 2, and the 1. So, grouping these together gives us

(-5w^2+4w^2-2w^2)+(-5w+2w+3w)+(3+2+1), which is equal to -5w^2+4w^2-2w^2=-3w^2.