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Ex.3: The area bounded by the parabola [tex]y^2 = x[/tex] along the X-axis and the lines [tex]x = 0[/tex] and [tex]x = 2[/tex] is _______ sq. units.

(A) [tex]\frac{4}{3}[/tex]
(B) [tex]\frac{4 \sqrt{2}}{3}[/tex]
(C) [tex]\frac{2}{3}[/tex]
(D) [tex]\frac{2 \sqrt{2}}{3}[/tex]


Sagot :

To find the area bounded by the parabola [tex]\( y^2 = x \)[/tex] along the X-axis and the lines [tex]\( x = 0 \)[/tex] and [tex]\( x = 2 \)[/tex], we will follow these steps:

1. Express the curve [tex]\( y^2 = x \)[/tex] as [tex]\( y \)[/tex] in terms of [tex]\( x \)[/tex]:
[tex]\[ y = \sqrt{x} \][/tex]

2. Set up the definite integral for the area:
The area under the curve [tex]\( y = \sqrt{x} \)[/tex] from [tex]\( x = 0 \)[/tex] to [tex]\( x = 2 \)[/tex] can be found using the definite integral:
[tex]\[ \text{Area} = \int_{0}^{2} \sqrt{x} \, dx \][/tex]

3. Evaluate the integral:
We need to find the antiderivative of [tex]\( \sqrt{x} \)[/tex]. Recall that [tex]\( \sqrt{x} \)[/tex] can be written as [tex]\( x^{1/2} \)[/tex]. The integral of [tex]\( x^{1/2} \)[/tex] is:
[tex]\[ \int x^{1/2} \, dx = \int x^{1/2} \, dx = \frac{2}{3} x^{3/2} + C \][/tex]
where [tex]\( C \)[/tex] is the constant of integration.

4. Apply the limits of integration:
[tex]\[ \left[ \frac{2}{3} x^{3/2} \right]_{0}^{2} \][/tex]

5. Calculate the definite integral:
[tex]\[ \frac{2}{3}(2^{3/2}) - \frac{2}{3}(0^{3/2}) \][/tex]
Simplifying [tex]\( 2^{3/2} \)[/tex], we get:
[tex]\[ 2^{3/2} = (\sqrt{2})^3 = 2\sqrt{2} \][/tex]
Therefore:
[tex]\[ \frac{2}{3} \cdot 2\sqrt{2} - 0 = \frac{4\sqrt{2}}{3} \][/tex]

So, the area bounded by the parabola [tex]\( y^2 = x \)[/tex] along the X-axis and the lines [tex]\( x = 0 \)[/tex] and [tex]\( x = 2 \)[/tex] is:
[tex]\[ \boxed{\frac{4\sqrt{2}}{3}} \][/tex]

This corresponds to option (B).