Question

Given the area, find the dimension of a rectangle

The length of a rectangle is 12m less than three times its width, its area is 63 square meters.​

Answer 1

Width W = 7 m

Length L = 9 m

Explanation:

Area of a rectangle = L * W

Area = 63 m²

L = 3W - 12

Area = L * W

66 = (3W - 12) * W

63 = 3W² - 12W

3W² - 12W - 63 = 0 ( solve W by using quadratic equation)

-(-12) ± √ -12² - 4 * 3 * (-63)

W = -------------------------------------------

2 * 3

W = 7 ; W = - 3

therefore use W = 7 m

solve for L:

L = 3W - 12

L = 3(7) - 12

L = 9 m

check:

Area = L * W

63 = 9 * 7

63 = 63 ----- OK