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The area of the region bounded by the parabola y2=8xy^2 = 8x and its latus rectum in the first quadrant, is

Solution

✅ Correct Option: 4

Given parabola: y2=8xy^2 = 8x

Comparing with the standard form y2=4axy^2 = 4ax:

4a=84a = 8

a=2a = 2

The latus rectum is the vertical line x=a=2x = a = 2


To find where the latus rectum meets the parabola, substitute x=2x = 2:

y2=8(2)=16y^2 = 8(2) = 16

y=4y = 4 (in the first quadrant)

The region is bounded by the parabola from x=0x = 0 to x=2x = 2, the latus rectum at x=2x = 2, and the x-axis.


From y2=8xy^2 = 8x:

y=8x=22xy = \sqrt{8x} = 2\sqrt{2x} (positive in first quadrant)

Area =∫02y dx= \int_0^2 y \, dx

=∫0222x dx= \int_0^2 2\sqrt{2x} \, dx

=22∫02x dx= 2\sqrt{2} \int_0^2 \sqrt{x} \, dx

=22⋅[x3/23/2]02= 2\sqrt{2} \cdot \left[\frac{x^{3/2}}{3/2}\right]_0^2

=22⋅23⋅[x3/2]02= 2\sqrt{2} \cdot \frac{2}{3} \cdot [x^{3/2}]_0^2

=423⋅(23/2−0)= \frac{4\sqrt{2}}{3} \cdot (2^{3/2} - 0)

=423⋅22= \frac{4\sqrt{2}}{3} \cdot 2\sqrt{2}

=8⋅23= \frac{8 \cdot 2}{3}

=163= \frac{16}{3} square units

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