Greatest Common Factor and Factor by Grouping: example 7.4

Find the GCF of: $21 x^{3}, 9 x^{2}, 15 x$ .

Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.

Your turn

The book's Try It right after this example: same idea, new numbers. Only the answer is given.

Find the greatest common factor: $25 m^{4}, 35 m^{3}, 20 m^{2}$ .

How did it go?

Factor each coefficient into primes and write the variables with exponents in expanded form. Circle the common factors in each column.
Bring down the common factors.
Multiply the factors.
	The GCF of $21 x^{3}$ , $9 x^{2}$ and $15 x$ is $3 x .$

Factor each coefficient into primes and write the variables with exponents in expanded form. Circle the common factors in each column.
Bring down the common factors.
Multiply the factors.
	The GCF of $21 x^{3}$ , $9 x^{2}$ and $15 x$ is $3 x .$