
Chloe S. answered 09/16/20
Patient & Bright Tutor for Math/Science/English/Spanish/SAT Prep
Let area = A, length = L, width = W. We are asked to find the dimensions, which are L and W.
Start with what we do know:
A = L*W
A = 55ft2
Therefore, L*W = 55ft2
We are told that length, L, is one more than twice the width, W. Therefore,
L = 1 + 2W
Now that we have written L in terms of W, we can substitute it into our equation for area and solve for W.
A = (1 + 2W)*W
Multiply each term in the parentheses by W.
A = 1*W + (2W)*W
A = W + 2W2
We know our value for area:
55ft2 = W + 2W2
From here, we see that we have a quadratic equation for which we can solve for W, either by using the quadratic formula or by factoring.
To get our equation into quadratic form of Ax2 + Bx + C = 0, we must subtract 55ft2 from each side:
2W2 + W - 55ft2 = 0
Option 1: Solve for W by factoring.
Since our first term coefficient A = 2, it is easiest to multiply 2 by our constant, -55.
2 * -55 = -110. We will then find the two factors of -110 that, when added together, equal our middle term coefficient B = 1. Some factors of -110:
-110 and 1, -55 and 2, -22 and 5, -11 and 10, -10 and 11.
The only two factors that add together to make our middle coefficient B are -10 and 11 (because -10 + 11 = 1).
We can now rewrite our equation substituting -10 + 11 for B = 1.
2W2 - 10W + 11W - 55 = 0
Next, we finish factoring by pulling out like terms:
(2W2 - 10W) + (11W - 55) = 0
= 2W(W - 5) + 11(W - 5)
= (2W + 11) * (W - 5) = 0
Since either one or both terms must be zero in order for their product to be zero, we can set each term equal to 0 to solve for W.
2W + 11 = 0 W - 5 = 0
2W = -11 W = 5
W = -11/2 = -5.5 W = 5
Option 2: Solve for W with quadratic formula
x = [-B ± √(B2 - 4AC)] ÷ 2A
= [-1 ± √(12 - 4(2)(-55))] ÷ 2(2)
= [-1 ± √(1 - -440)] ÷ 4
= (-1 ± 21) ÷ 4
= (-1 + 21) ÷ 4 = (-1 - 21) ÷ 4
= 5 = -5.5
We know that our width W cannot be a negative value, so our correct value for width is W = 5ft. (Note that we dropped units until now for the sake of more easily solving for W, but we cannot forget to bring units back in).
Now we can solve for length by substituting for W.
L = 1 + 2W
L = 1ft + 2*5ft
L = 1ft + 10ft
L = 11ft
We can check our work by testing A = L*W: A = 55ft2 = 5ft * 11ft
Thus, our dimensions are L = 11ft and W = 5ft, so 11ft by 5 ft.