Question 120738
First of all, notice what each term has in common:
a multiple of {{{3a}}}
factor that out: {{{(3a)(x^2-14+5x)}}}={{{(3a)(x^2+5x-14)}}}

For factoring {{{x^2+5x-14}}}, we list the possible numbers that multiply to 14:
1, 2, 7, 14.
Which two of these, when taking one negative, add to get +5? -2 and +7!

Thus, {{{x^2+5x-14}}} factors to {{{(x+7)(x-2)}}}, which makes the final expression:

{{{3a(x+7)(x-2)}}}