Question

Factor Completely: 3x^2 − 21

3(x2 − 7)

3(x + 7)(x − 7)

3(x + 7)(x − 3)

Prime

Answer 1

What is common in this?

Answer 2

3 x 1=3
2 x 7=21

So.
3(x^2-7)

Answer 3

3(x^2-7)