A rectangle is 3 cm longer than it is wide. The diagonal is 15 cm. Find the dimensions of the rectangle?

The length is 12 cm, and the width is 9 cm.

Step-by-step explanation:

The length and width of a rectangle as legs form a right triangle with the diagonal of the triangle as the hypotenuse.

We can use the Pythagorean theorem to write an equation.

Let the width = w = leg a

The length = w + 3 = leg b

The diagonal = the hypotenuse = 12 = c

a^2 + b^2 = c^2

w^2 + (w + 3)^2 = 15^2

w^2 + w^2 + 6w + 9 = 225

2w^2 + 6w - 216 = 0

w^2 + 3w - 108 = 0

(w + 12)(w - 9) = 0

w + 12 = 0   or   w - 9 = 0

w = -12   or   w = 9

Since a width cannot be a negative number, we discard the solution w = -12.

width = w = 9

length = w + 3 = 9 + 3 = 12

The length is 12 cm, and the width is 9 cm.

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step-by-step explanation:

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