Antonia is factoring the polynomial, which has four terms.

21x3−63x2+15x−45

3[7x3−21x2+5x−15]

3[7x2(x−3)+5(x−3)]

Which is the completely factored form of her polynomial?

21x2(x − 3)
36x2(x − 3)
3(7x2 + 5) (x − 3)
3(12x2 + 5) (x − 3)