How do you factor completely #3x^2 − 21#?

1 Answer
Oct 4, 2016

Answer:

rational factors #3(x^2-7)#
irrational facors #3(x+sqrt7)(x-sqrt7)#

Explanation:

Always look for a common factor first.

#3x^2 -21" "larr# there is a common factor of 3

#3(x^2 -7)" "larr# there are no other rational factors

However, as this is in the form of the difference of squares, we could show irrational factors as:

#3(x+sqrt7)(x-sqrt7)#