Question:medium

The area of the region bounded by the curve $y^2 = x^3$, the y-axis and the lines $y = 1$ and $y = 8$ is

Show Hint

When calculating areas bounded by the y-axis and horizontal lines ($y=c$ to $y=d$), always rewrite the function as $x = f(y)$ and integrate with respect to $dy$. This avoids having to split the integral into multiple parts or dealing with more complex inverse functions if you tried integrating with respect to $dx$.
Updated On: Apr 29, 2026
  • $\frac{155}{3}$ sq. units
  • $\frac{93}{5}$ sq. units
  • $93$ sq. units
  • $155$ sq. units
Show Solution

The Correct Option is B

Solution and Explanation

To solve this problem, we need to find the area of the region bounded by the curve \( y^2 = x^3 \), the y-axis, and the horizontal lines \( y = 1 \) and \( y = 8 \).

  1. First, interpret the given curve equation \( y^2 = x^3 \). Solving for \( x \) in terms of \( y \), we have \( x = y^{2/3} \).
  2. Since the region is bounded by the y-axis, we consider only the part of the graph where \( x = y^{2/3} \) from \( y = 1 \) to \( y = 8 \).
  3. We need to integrate \( x = y^{2/3} \) with respect to \( y \) from \( y = 1 \) to \( y = 8 \) to find the area. This is because the area under the curve from the y-axis involves integrating along \( y \), not \( x \).
  4. Set up the integral to find the area:

\(A = \int_{1}^{8} y^{2/3} \, dy\)

  1. Compute the integral:

\(\int y^{2/3} \, dy = \frac{y^{5/3}}{5/3} = \frac{3}{5} y^{5/3}\)

  1. Evaluate this from \( y = 1 \) to \( y = 8 \):

\(A = \left[\frac{3}{5} y^{5/3}\right]_{1}^{8} = \frac{3}{5} \left( 8^{5/3} - 1^{5/3} \right)\)

  1. Simplify the expression:

Calculate \( 8^{5/3} \):

  1. \( 8^{1/3} = 2 \), because the cube root of 8 is 2.
  2. \( 2^5 = 32 \). Therefore, \( 8^{5/3} = 32 \).

Now calculate:

\(A = \frac{3}{5} \left( 32 - 1 \right) = \frac{3}{5} \times 31 = \frac{93}{5}\)

  1. This value matches the correct answer in the options.

Therefore, the area of the region bounded by the given curve, the y-axis, and the lines \( y = 1 \) and \( y = 8 \) is \(\frac{93}{5}\) square units.

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