Area funeria

Geometry Level 3

Find the area of the region enclosed by the graph of \text{Find the area of the region enclosed by the graph of} x 60 + y = x 4 . |x-60|+|y|=\left|\dfrac{x}{4}\right|.

ALso Try this


The answer is 480.

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1 solution

Parth Lohomi
Mar 10, 2015

Since y |y| is nonnegative, x 4 x 60 \left|\frac{x}{4}\right| \ge |x - 60| . Solving this gives us two equations: x 4 x 60 a n d x 4 x 60 \frac{x}{4} \ge x - 60\ \mathrm{and} \ -\frac{x}{4} \le x - 60 . Thus, 48 x 80 48 \le x \le 80 . The maximum and minimum y value is when x 60 = 0 |x - 60| = 0 , which is when x = 60 x = 60 and y = ± 15 y = \pm 15 . Since the graph is symmetric about the y-axis, we just need casework upon x x . x 4 > 0 \frac{x}{4} > 0 , so we break up the condition x 60 |x-60| :

\implies x 60 > 0 x - 60 > 0 . Then y = 3 4 x + 60 y = -\frac{3}{4}x+60 .

\implies x 60 < 0 x - 60 < 0 . Then y = 5 4 x 60 y = \frac{5}{4}x-60 .

The area of the region enclosed by the graph is that of the quadrilateral defined by the points ( 48 , 0 ) , ( 60 , 15 ) , ( 80 , 0 ) , ( 60 , 15 ) (48,0),\ (60,15),\ (80,0), \ (60,-15) . Breaking it up into triangles and solving, we get 2 1 2 ( 80 48 ) ( 15 ) = 480 2 \cdot \frac{1}{2}(80 - 48)(15) = \boxed{480}

Q.E.D

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