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The area enclosed between the graph of y = x³ and the lines x = 0, y = 1, y = 8 is

Solution

Correct Option: 3

The region is bounded by:

  • The curve y=x3y = x^3
  • The y-axis (line x=0x = 0)
  • Horizontal line y=1y = 1 (bottom boundary)
  • Horizontal line y=8y = 8 (top boundary)

When y=1y = 1: x3=1x^3 = 1x=1x = 1

When y=8y = 8: x3=8x^3 = 8x=2x = 2

The region is between the y-axis (left side) and the curve (right side), from y=1y = 1 to y=8y = 8.


Since the boundaries are horizontal lines (y=1y = 1 and y=8y = 8), integrate with respect to yy.

From y=x3y = x^3, taking the cube root:

x=y1/3x = y^{1/3}


Area =18= \int_1^8 (width) dydy

Width at any height yy is the distance from y-axis to curve =x0=y1/3= x - 0 = y^{1/3}

Area =18y1/3dy= \int_1^8 y^{1/3} dy


Using the power rule:

y1/3dy=y1/3+11/3+1\int y^{1/3} dy = \dfrac{y^{1/3 + 1}}{1/3 + 1}

=y4/34/3= \dfrac{y^{4/3}}{4/3}

=34y4/3= \dfrac{3}{4}y^{4/3}


Area =34[y4/3]18= \dfrac{3}{4}[y^{4/3}]_1^8

=34[84/314/3]= \dfrac{3}{4}[8^{4/3} - 1^{4/3}]

Since 84/3=(83)4=24=168^{4/3} = (\sqrt[3]{8})^4 = 2^4 = 16:

=34[161]= \dfrac{3}{4}[16 - 1]

=34×15= \dfrac{3}{4} \times 15

=454= \dfrac{45}{4} square units

Therefore, the area enclosed is 454\dfrac{45}{4} square units.

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