Sketch the region enclosed by the given curves. y = |9x|, y = x2 - 10
Solution:
Given, the curves are y = |9x|, y = x2 - 10
y = |9x| is a huge V passing through (-1, 9), origin is min point and (1, 9).
y = x2 - 10 is the classical parabola y = x2 but translated -10points downwards so that the absolute min point is (0, -10).
Both curves are symmetric with respect to vertical y axis,
For x > 0, the intersection point is
9x = x2 - 10
On rearranging,
x2 - 9x - 10 = 0
x2 -10x + x - 10 = 0
x(x - 10) + 1(x - 10) = 0
(x + 1)(x - 10) = 0
x = 10 or -1
When x = 10, y = 9(10) = 90
When x = -1, y = 9(-1) = -9
Area is the integral of the difference = \(\int_{-1}^{10}(\left | 9x \right |-(x^{2}-10))dx\)
= \(\int_{-1}^{10}(9x-x^{2}+10)dx\)
= \([9\frac{x^{2}}{2}-\frac{x^{3}}{3}+10x]_{-1}^{10}\)
= \([9\frac{(10)^{2}}{2}-\frac{(10)^{3}}{3}+10(10)]-[9\frac{(-1)^{2}}{2}-\frac{(-1)^{3}}{3}+10(-1)]\)
= \([\frac{(900)}{2}-\frac{(1000)}{3}+100]-[\frac{9}{2}+\frac{1}{3}-10]\)
= \([\frac{2700-2000+600}{6}]-[\frac{27+2-60}{6}]\)
= \([\frac{1300}{6}]-[\frac{-31}{6}]\)
= \([\frac{1331}{6}]\)
Therefore, the area is 1331/6 square units.
Sketch the region enclosed by the given curves. y = |9x|, y = x2 - 10
Summary:
The region enclosed by the given curves. y = |9x|, y = x2 - 10 is 1331/6 square units.
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