the width of the rectangle is the length minus 4 units. the area of the rectangle is 21 units. what is the width, in units, of the rectangle?

Answer 1

Area = LxW.

Given: A=21u² and W = L-4.

Using given information, A = LxW = Lx(L-4) = L² - 4L

21 = L² - 4L. Subtract 21 from both sides

0 = L² - 4L - 21.

From quadratic formula, a=1, b = -4 and c = -21.

Applying the formula one can find that (L - 7) x (L + 3) provides the solution L = 7 units. (Note L = -3 is a solution as well, but it is impossible in this context).

L = 7 and W = L-4 = 3 units.

Answer 2

The equation to find the area of a rectangle is length (l) * width (w) = Area. So we want to find 2 #s that can multiply into 21 yet the differences between them is 4. I tried 7*3=21. The answer fit both criteria and therefore, the width is 3 units.