Question

Factor Completely: 3x2 − 21

3(x2 − 7)

3(x + 7)(x − 7)

3(x + 7)(x − 3)

Prime

Answer 1

You cannot factor 7, since it is not a perfect square. You did the first step right, 3(x^2-7)m and that would be your final answer

Answer 2

The first one because after taking out the 3 you get 3(x^2 - 7) and -7 doesn't have a whole number square root.