WEBVTT

1
00:00:00.000 --> 00:00:03.344
Here is the problem: (a plus 2b)(a minus 2b).

2
00:00:03.794 --> 00:00:08.206
Expand (a plus 2b)(a minus 2b) and collect like terms.

3
00:00:09.006 --> 00:00:10.202
Read the expression.

4
00:00:10.652 --> 00:00:19.789
Distribute (multiply out every product). Each term in one factor multiplies each term in the other: a(b plus c) equals ab plus ac.

5
00:00:20.239 --> 00:00:22.201
Result after multiplying out.

6
00:00:22.651 --> 00:00:32.148
Combine like terms. ab: negative 2 plus 2 equals 0. Like terms have identical variables and exponents, so only their coefficients are added.

7
00:00:32.948 --> 00:00:37.650
Write the result in standard form. Terms are ordered by descending total degree.

8
00:00:38.450 --> 00:00:41.701
So the answer is a squared minus 4b squared.

9
00:00:42.151 --> 00:00:50.940
After expanding and combining like terms the expression is a squared minus 4b squared, a polynomial of degree 2 with 2 terms.

10
00:00:51.740 --> 00:01:05.451
Spot check at a equals 0.73, b equals 1.14: original negative 4.6655, simplified negative 4.6655, which checks out.