✔ 最佳答案
First look for the GCF (greatest common factor). Since all the terms are even, the GCF is 2. Now you have the following:
2(3x^2 - 14x - 24)
Forget about the 2 outside the parentheses for a while. You need two numbers that, when added, give you -14 (the middle number) and when multiplied give you -72 (the product of the first and last numbers).
Several pairs of numbers multiply to be 72 (we'll deal with the negative sign momentarily): 1 & 72, 2 & 36, 3 & 24, 4 & 18, 6 & 12, and 8 & 9. Since 4 and 18 differ by 14, that is the correct choice. But, one term must be negative so the product is -72. It's either -4 & 18 or 4 & -18. Since the sum must be -14, the two numbers are 4 & -18.
Now rewrite the middle term as + 4x - 18x. You now have the following:
3x^2 + 4x - 18x - 24
The first two terms have an x in common, and the last two terms have a 6 in common. Factor these out:
x(3x + 4) - 6(3x + 4)
Notice that I factored a -6 out of the last two terms. That made the 4 change to a positive.
Since both factors have a (3x + 4), it can be factored out:
(3x + 4)(x - 6)
But don't forget about the 2!
2(3x + 4)(x - 6)
Hope this helps!