Let the area of the bounded region \(x, y) : 0 9x y2, y 3x - 6 \ be A. Then 6A is equal to .
Answer
15
Solution
0 9x y2 x 0 and the point lies outside (or on) the parabola y2 = 9x, i.e. y 3 x or y -3 x.
y 3x - 6: the point lies above the line y = 3x - 6.
Line and parabola meet where y2 = 3(y + 6) y2 - 3y - 18 = 0 y = -3, 6, i.e. at (1, -3) and (4, 6).
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The part above y = 3 x is unbounded; the bounded part lies between y = 3x - 6 and y = -3 x for 0 x 1.
A = 01 [-3 x - (3x - 6) ] dx
= [-2x 32 - 3x22 + 6x ]01
= -2 - 32 + 6 = 52
6A = 15
Answer: 15