How do you factor by grouping mn - 4m - 5n + 20?

2 Answers
George C.
May 25, 2015

mn-4m-5n+20

= (mn-4m)-(5n-20)

=m(n-4)-5(n-4)

=(m-5)(n-4)

Alan P.
May 25, 2015

Given mn-4m -5n+20
Notice that by extracting a common factor from the first 2 terms and a (different) common factor from the last 2 terms, we are left with (n-4) in both cases;
so
color(red)(mn-4m) color(blue)(-5n+20)

=color(red)(m(n-4))color(blue)(-5(n-4))

=(m-5)(n-4)

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