Factor out the GCF of from each term in the polynomial.

Factor out the GCF of from the expression .

Factor out the GCF of from the expression .

Factor out the GCF of from the expression .

Factor out the GCF of from the expression .

Since all the terms share a common factor of , it can be factored out of each term.

Group the first two terms and the last two terms.

Factor out the greatest common factor (GCF) from each group.

Factor the polynomial by factoring out the greatest common factor, .

Factor by Grouping 21k^3-84k^2+15k-60