 factoring by grouping. How do we factor something of this form? Now we see that these first two terms have a in common, the last three terms have two in common, the first and third term have a b in common, so let's see if we group a and b, a b plus 2 b, and we also group 2 a c plus 4 c. Now we can pull out a b on here, a plus 2, on here we can pull out a 2 c, and inside we can have a plus 2. Now these two terms have a common factor, namely a plus 2, so we can pull out that common factor and what's left from the first term is b and from the second term is 2 c. Let us look at a second example. Well here I'm going to group these two and these two. I'm going to pull out 2x squared and then an x is left inside plus 1, then here I'm going to pull out negative 3, and inside we'll end up with x plus 1. Yes now we have a common factor, a common factor from those terms that we can pull out from the first term 2x squared remains and from the second term 3.