i need help i don't know how to do the next step.

factor by grouping

x^3-3x^2+4x-12

so what i have so far is this

=(x^3-3x^2)+(4x-12)
=x(x^2-3x)+4(x-3)
from here i don't know...

and then this one is driving me insane this next one...

Rewrite the middle term as the sum of two terms and then factor by grouping.

x^2-14x+45

i'd figure out problem #1
these are the steps I did:
factor by grouping

x^3-3x^2+4x-12

so what i have so far is this

=(x^3-3x^2)+(4x-12)
=x^2(x-3)+4(x-3)
= (x-3)(x^2+4)

I AM STILL HAVING TROUBLE WITH PROBLEM NUMBER 2

to your second question

wouldnt it be-
(x-5)(x-9)

You have to find 2 numbers to multiply to bed 45 BUT add to be negative 14.

yes,thank you......