Elementary Technical Mathematics

Published by Brooks Cole
ISBN 10: 1285199197
ISBN 13: 978-1-28519-919-1

Chapter 11 - Section 11.1 - Solving Quadratic Equations by Factoring - Exercise - Page 364: 31

Answer

Base = $12$ m Height = $11$ m

Work Step by Step

We know the following; Area of triangle = $66 m^2$ Base = $(x+1)$ Height = $x$ The formula for the area of a triangle is $\frac{1}{2}\times base \times height$. We can substitute the values we know into the formula for area to get a quadratic equation. Area = $\frac{1}{2}\times base \times height$ 66 = $\frac{1}{2}\times (x+1) \times x$ 66 = $\frac{x^2+x}{2}$ (Multiply both sides by 2) $132 = x^2+x$ (Subtract 132 from each side to make it equal 0) $x^{2}+x-132=0$ We now have our quadratic equation, which we can solve by factoring! $x^{2}+x-132=0$ $x^{2}+12x-11x-132=0$ $x(x+12)-11(x+12)=0$ $(x-11)(x+12)=0$ To find the solutions for $x$, we can make both brackets = 0. $(x-11)=0$ or $(x+12)=0$ $x=11$ or $x=-12$ $x$ cannot be a negative value in this case, as we are talking about the height of a triangle, which cannot be below 0. So, $x=11$. We can now find the base and height of the triangle. Base = $(11+1)$ = $12$ m Height = $11$ m
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