Patrick A. answered 04/23/20
High School and College Mathematics Tutoring
We are given that the area is
A = 16x2 + 20x
But, we also know
A = (width)(length)
and length = 4x
By combining our equations and substituting our variable expression for the length we get
16x2 + 20x = (width)(4x)
Divide both sides by 4x to get
width = (16x2 + 20x)/(4x)
Recall that (A+B)/C = A/C + B/C or more concretely, (1+2)/3 = 1/3 + 2/3
We apply that to get
width = (16x2 + 20x)/(4x)
width = (16x2)/(4x) + (20x)/(4x)
width = 4x + 5