Introductory Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-805-X
ISBN 13: 978-0-13417-805-9

Chapter 9 - Cumulative Review Exercises - Page 686: 50

Answer

For this rectangle, the length is $11$ meters and the width is $5$ meters.

Work Step by Step

We know that the area of a rectangle can be given by the following formula: $$A = lw$$ where $A$ is the area, $l$ is the length, and $w$ is the width. We have the area for this rectangle as $55$ square meters, and the length is $6$ meters more than the width, so if we have $w$ as the width, then the length $l$ is $w + 6$. We can plug these values into the equation for area: $$55 = (w + 6)(w)$$ We use the distributive property to simplify the right side of the equation: $$55 = w(w) + 6(w)$$ We multiply to simplify: $$55 = w^2 + 6w$$ We can turn this into a quadratic equation and set it to $0$ to solve for $w$: $$w^2 + 6w - 55 = 0$$ To factor this equation, we need to see what combination of factors for the constant $-55$ when added together will give us $6$, the coefficient of the second term. We will want to find one negative factor and one positive factor where the positive factor is a greater number than the negative factor. Let's look at the factors: $-55$ and $1$ or $55$ and $-1$ $-11$ and $5$ or $11$ and $-5$ It seems like the factors $11$ and $-5$ will work, so we plug these into the equation: $$(w + 11)(w - 5) = 0$$ According to the Zero Product Property, either factor can equal zero, so we set each factor equal to zero to solve for $w$: $$w + 11 = 0$$ Subtract $11$ from each side to solve for $w$: $$w = -11$$ We set the other factor equal to $0$: $$w - 5 = 0$$ Add $5$ to each side to solve for $w$: $$w = 5$$ Since measurements cannot be negative, we discard the $-11$ answer, so we know that the width is $5$ meters. If the width is $5$ meters, we can plug this value into the equation for area and solve for length: $$55 = (l)(5)$$ Divide both sides by $5$ to solve for $l$: $$l = 11$$ For this rectangle, the length is $11$ meters and the width is $5$ meters.
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