Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section A

Chapter

Application of Integrals

Question:

Find the area in the planar bounded by the curves y = x -1 and (y - 1)2 = 4(x + 1).

Options:

$\frac{5}{3}$

$\frac{10}{3}$

$\frac{11}{3}$

$\frac{64}{3}$

Correct Answer:

$\frac{64}{3}$

Explanation:

Eliminating y we get the points of intersection as

$(x-2)^2=4(x+1)$

or x2 - 8x = 0

∴ x = 0, 8   ∴ y = -1, 7

Hence the points of intersection are (0, –1) and (8, 7). The vertex of the parabola is at the point (–1, 1).

The line cut axes at (1, 0) and (0, –1)

$A=\int_{-1}^{7}(x_1-x_2)dy=\int_{-1}^{7}[(y+1)-\{\frac{(y-1)^2}{4}-1\}]dy=\{\frac{1}{2}y^2+y-\frac{(y-1)^3}{12}+y\}_{-1}^{7}=\frac{64}{3}$