Q75 / 180 · COMEDK 2026 (9 May Shift 1) · Mathematics
The area of the region bounded by the line $y = x + 2$ and the curve $x = -y^2$ is
- Correct answerA$4.5\ \text{sq units}$
- B$13.5\ \text{sq units}$
- C$\dfrac{7}{6}\ \text{sq units}$
- D$2.5\ \text{sq units}$
Solution
The given curves are $x = -y^2$ and $y = x + 2$.
To find the points of intersection, substitute $x = y - 2$ into the equation of the parabola:
$y - 2 = -y^2$
$y^2 + y - 2 = 0$
$(y + 2)(y - 1) = 0$
The points of intersection are at $y = -2$ and $y = 1$.
The area of the bounded region is given by integrating the difference of the right curve $x = -y^2$ and the left curve $x = y - 2$ with respect to $y$ from $y = -2$ to $y = 1$:
$A = \int_{-2}^{1} (-y^2 - (y - 2)) \, dy$
$A = \int_{-2}^{1} (-y^2 - y + 2) \, dy$
Integrating the expression:
$A = \left[ -\dfrac{y^3}{3} - \dfrac{y^2}{2} + 2y \right]_{-2}^{1}$
Substituting the upper limit $y = 1$:
$-\dfrac{1}{3} - \dfrac{1}{2} + 2 = \dfrac{-2 - 3 + 12}{6} = \dfrac{7}{6}$
Substituting the lower limit $y = -2$:
$-\dfrac{(-2)^3}{3} - \dfrac{(-2)^2}{2} + 2(-2) = \dfrac{8}{3} - 2 - 4 = -\dfrac{10}{3}$
Calculating the total area:
$A = \dfrac{7}{6} - \left( -\dfrac{10}{3} \right) = \dfrac{7}{6} + \dfrac{20}{6} = \dfrac{27}{6} = 4.5$
Answer: $4.5\ \text{sq units}$
To find the points of intersection, substitute $x = y - 2$ into the equation of the parabola:
$y - 2 = -y^2$
$y^2 + y - 2 = 0$
$(y + 2)(y - 1) = 0$
The points of intersection are at $y = -2$ and $y = 1$.
The area of the bounded region is given by integrating the difference of the right curve $x = -y^2$ and the left curve $x = y - 2$ with respect to $y$ from $y = -2$ to $y = 1$:
$A = \int_{-2}^{1} (-y^2 - (y - 2)) \, dy$
$A = \int_{-2}^{1} (-y^2 - y + 2) \, dy$
Integrating the expression:
$A = \left[ -\dfrac{y^3}{3} - \dfrac{y^2}{2} + 2y \right]_{-2}^{1}$
Substituting the upper limit $y = 1$:
$-\dfrac{1}{3} - \dfrac{1}{2} + 2 = \dfrac{-2 - 3 + 12}{6} = \dfrac{7}{6}$
Substituting the lower limit $y = -2$:
$-\dfrac{(-2)^3}{3} - \dfrac{(-2)^2}{2} + 2(-2) = \dfrac{8}{3} - 2 - 4 = -\dfrac{10}{3}$
Calculating the total area:
$A = \dfrac{7}{6} - \left( -\dfrac{10}{3} \right) = \dfrac{7}{6} + \dfrac{20}{6} = \dfrac{27}{6} = 4.5$
Answer: $4.5\ \text{sq units}$
Hence, the correct answer is option: 'A'.