Exercise 30 Page 69

To factor by grouping, we will take the greatest common factor of the first pair of terms and the greatest common factor of the second pair of terms.

2r^3 - r^2-72r+36

FactorOut

Factor out r^2

r^2(2r-1) - 72r + 36

FactorOut

Factor out - 36

r^2(2r-1)-36(2r-1)

Notice that (2r-1) is a factor of both terms, so we can factor it out.

r^2(2r-1)-36(2r-1)

FactorOut

Factor out ( 2r-1 )

( 2r-1 ) ( r^2-36 )

FacDiffSquares

a^2-b^2=(a+b)(a-b)

(2r-1)(r+6)(r-6)