Answer
The length is (6x+15)
Work Step by Step
Area is Length $\times$ width.
The given area is $18x^{2}$ + 69x + 60. And the width is 3x + 4.
When we use FOIL to simplify we follow. FOIL: First (Multiply the first variables in the brackets), outside (Multiply the outer variables), Inside (Multiply the inside variables), Last (Multiply the last variables in the brackets).
So:
(ax+b)(cx+d) the number in front of $x^{2}$ is a$\times$ c And since one of the numbers is 3 and the final ac is 18 thus the other number is $\frac{18}{3}$ = 6.
The last number in the polynomial is b$\times$ d. And since one of the numbers is 4 and the final bd is 60 thus the other number is $\frac{60}{4}$ = 15.
Therefore the length is (6x+15) as it is the other factor.
