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面积 4x+y^2=9,x=2y

解答

面积

4 x + y^{2} = 9, x = 2 y

解答

\frac{125}{3}

+1

十进制

41.66666 \dots

求解步骤

对于

4 x + y^{2} = 9

将

y

移到一边:

y = 9 - 4 x, y = - 9 - 4 x

对于

x = 2 y

将

y

移到一边:

y = \frac{x}{2}

f_{1} (x) = 9 - 4 x

f_{2} (x) = - 9 - 4 x

要找到相交点，解

f_{i} (x) = f_{j} (x)

9 - 4 x = - 9 - 4 x : x = \frac{9}{4}

9 - 4 x = \frac{x}{2} : x = 2

- 9 - 4 x = \frac{x}{2} : x = - 18

= \int_{- 18}^{2} ∣ f_{2} (x) - f_{3} (x) ∣ d x + \int_{2}^{\frac{9}{4}} ∣ f_{1} (x) - f_{2} (x) ∣ d x

= \int_{- 18}^{2} - 9 - 4 x - \frac{x}{2} d x + \int_{2}^{\frac{9}{4}} 9 - 4 x - (- 9 - 4 x) d x

\int_{- 18}^{2} - 9 - 4 x - \frac{x}{2} d x = \frac{124}{3}

\int_{2}^{\frac{9}{4}} 9 - 4 x - (- 9 - 4 x) d x = \frac{1}{3}

= \frac{124}{3} + \frac{1}{3}

化简

= \frac{125}{3}

作图

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