Answer:
3x(2x + 7)
Explanation:
Simply put, take out what is repetitive in the equation
x is repetitive so that will be taken out
LCM of 6 and 21 is 3 so that will also be taken out
When taken out, the factors you've taken out will have to be outside of the parentheses, so you keep the original expression, but the factors you take out will be outside. The factors of this problem is 3 and x
Start with x
x(6x + 21)
Now do 3
3x(2x + 7)