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

2 Answers
Ratnaker Mehta
Jun 29, 2016

Expression=3x^2(7x-6)+1(7x-6)=(7x-6)(3x^2+1).

Explanation:

Observe that 3x^2 can be taken out as common from the first two terms, 7, from the last two terms, only 1 can be taken out. Hence,

Expression=3x^2(7x-6)+1(7x-6)=(7x-6)(3x^2+1).

Jim G.
Jun 29, 2016

(7x-6)(3x^2+1)

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)

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