First, we know the formula for area is:
Area = Length* Width
Therefore, 128 = (3x+7)(x+5)
We can use the F.O.I.L method to multiply
- First: (3x *x )= 3x²
-Outer: (3x*5) = 15x
-Inner: (7*x) = 7x
-Last: (7*5) = 35
Now we add the sum → 3x² + 15x + 7x + 35 → 3x² + 22x + 35
3x²+ 22x + 35 = 128
3x²+ 22x -93 = 0
Now you have to factor to solve for the x value.
(3x+31)(x−3)
x = 3 & x = -31/3
The negative value is eliminated because u can't have a negative length.
The length is 3x+7
L= 3(3) +7
L= 9+7
L= 16