The area of the region bounded by the curve \(2y = 3x - 6\), y-axis and the line \(y = 2\) and \(y = -3\) is :
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \(\displaystyle\frac{25}{3}\) sq. units
The region lies between the y-axis and the line, from y = −3 to y = 2, so it is an area with respect to the y-axis: integrate x with respect to y.
\( \displaystyle 2y = 3x - 6 \;\Rightarrow\; x = \frac{2y + 6}{3} \)
For \(-3 \le y \le 2\), \(x \ge 0\) (x = 0 at y = −3), so the line stays on the right of the y-axis.
\( \displaystyle \text{Area} = \int_{-3}^{2} \frac{2y + 6}{3}\,dy \)
\( \displaystyle = \frac{1}{3}\left[y^2 + 6y\right]_{-3}^{2} \)
\( \displaystyle = \frac{1}{3}\left[(4 + 12) - (9 - 18)\right] \)
\( \displaystyle = \frac{1}{3}(16 + 9) = \frac{25}{3} \text{ sq. units} \)
Shortcut: The region is a triangle with vertices (0, −3), (0, 2) and \(\left(\frac{10}{3}, 2\right)\). Its base on the y-axis is 5 and its height is \(\frac{10}{3}\), so the area is \(\frac{1}{2} \times 5 \times \frac{10}{3} = \frac{25}{3}\).