# How do you factor #21x^3 - 18x^2 + 7x - 6# by grouping?

##### 2 Answers

Jun 29, 2016

Expression

#### Explanation:

Observe that

Expression

Jun 29, 2016

#### Explanation:

Group the terms in 'pairs' as follows.

#[21x^3-18x^2]+[7x-6]# now factorise each 'pair'.

#color(red)(3x^2)(7x-6)color(red)(+1)(7x-6)# We now have a common factor of (7x -6) in each pair which we can take out.

#(7x-6)(color(red)(3x^2+1))#

#rArr21x^3-18x^2+7x-6=(7x-6)(3x^2+1)#