Question 101907
21x^3 - 6x^2 + 15x

all the terms are divisible by 3, and by x, so just factor them out! to check to make sure if you're right, re-distribute the numbers

3x(7x^2 - 2x + 5) is your answer

to check...distribute!

21x^3 - 6x^2 + 15x

it comes back to your original people, meaning, the answer is correct