Question

21a + 9
the gcf of 21 and 9 is 3.
3 × \boxed{} = 21a
3 × \boxed{} = 9
the factored expression is \boxed{}.

Explanation:

Step1: Find the first missing term

To find the term that when multiplied by 3 gives \(21a\), we divide \(21a\) by 3. So, \(\frac{21a}{3} = 7a\).

Step2: Find the second missing term

To find the term that when multiplied by 3 gives 9, we divide 9 by 3. So, \(\frac{9}{3} = 3\).

Step3: Factor the expression

Using the distributive property \(ab + ac = a(b + c)\), we factor out the GCF (3) from \(21a + 9\). Substituting the values we found, we get \(3\times7a + 3\times3 = 3(7a + 3)\).

Answer:

First box: \(7a\)
Second box: \(3\)
Factored expression: \(3(7a + 3)\)