
>> Only three of these are actually fully factored, these three down here. 3x

plus 2 times 5x minus 3, x plus 1 times x minus 1, and surprisingly perhaps, 3

times the quantity x squared plus 1. In the first choice, the second factor, 6x

plus 9, is actually the same as 3 times the quantity 2x plus 3. So since we can

factor this more, it's not fully factored. Similarly, 10x minus 15 can be

factored to equal 5 times the quantity 2x minus 3. X squared minus 1, as we

learned earlier, can be factored as x plus 1 times x minus 1. And the expression

x squared minus 4x plus 4, which we see multiplied by 5 here, is the same as x

minus 2 squared.