Answer:
x = 5.
Explanation:
The area of a rectangle can be determined by the following formula.
A = l ⋅ w
l stands for length or the longer side.
w stands for width or the shorter side.
Now, we can plug the values we are given into the equation.
A = ( x − 2 ) ⋅ ( x + 8 )
The easiest way to multiply is to follow the acronym FOIL , which stands for First Outside Inside Last, and dictates the order in which you multiply these terms.
A = x 2 + 8 x − 2 x −16 = x 2 + 6 x − 16
Now, we can plug in the given value for the area.
39 = x 2 + 6 x − 16
Next, we simplify by moving all terms to one side and factor the equation.
0 = x 2 + 6 x − 55
Finally, we factor the equation. This means we reverse-FOIL, trying to determine the two things that we multiplied together.
0= ( x − 5 ) ⋅ ( x + 11 )
If the equation ultimately equals zero, either ( x − 5 ) or ( x + 11 ) or both equal zero. Therefore, we set each equal to zero to find the value of
x .
x − 5 = 0 x = 5 x + 11 = 0
x = − 11
Since x is a length, we know it cannot be negative. Thus, we can conclude that it equals 5.