00:01
Let's review some factoring.
00:02
For par a, we want to factor x cubed minus 3x squared, minus 25x, plus 75.
00:11
That's four terms.
00:13
Remember the grouping method.
00:16
You can take out an x squared from the first group left with x minus 3, and we can take out a negative 25 left with x minus 3.
00:25
The common group is x minus 3, and x squared minus 25.
00:31
To be factored completely, this is still a difference of squares.
00:36
So it's x minus 3 times x plus 5 times x minus 5 in no particular order.
00:44
For part b, 2x squared minus 13x minus 24.
00:52
It's a trinomial.
00:53
It can't greatest common factor anything.
00:56
So we have a target, multiply a and c.
00:59
2 times negative 24 is negative 48.
01:02
And it's going to add to negative 13, which just tells us that the product of these two numbers, one has to be positive, one has to be negative, and the larger one is negative, the bigger, the smaller one is positive...