Let be the bounded area enclosed by the curves , and -axis that lies in the first quadrant. Let be the bounded area enclosed by the curves , , and -axis that lies in the first quadrant. Then is equal to
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- D
Let be the bounded area enclosed by the curves , and -axis that lies in the first quadrant. Let be the bounded area enclosed by the curves , , and -axis that lies in the first quadrant. Then is equal to
Correct answer:D
Standard Method
Given: We need the bounded areas and in the first quadrant.
Find: The value of .
For , the region is bounded by , and . Their intersection is found from
so
which gives the first-quadrant point .
Hence,
For , the region is bounded by , , and the -axis. Using the working shown, change the variable to integrate with respect to :
Substituting from the shown relation gives
Now subtract:
From the provided solution, the final result is stated as
Therefore, the correct option is D.
Area Setup from Sketch
Given: Two bounded first-quadrant regions are formed by the stated curves.
Find: The required difference of areas.
The hint says to sketch the curves first. For , compare the line with the parabola between and their point of intersection . In this interval, the line lies above the parabola, so area is upper curve minus lower curve.
For , the solution uses integration with respect to . The right boundary is given by the relation used in the working, and the lower-to-upper limits come from to as written in the source solution. Evaluating that integral gives the stated expression for , and subtracting from leads to the final option D.
Taking the wrong upper and lower curves for is a common mistake. If you subtract from , the area becomes negative. Always sketch first and use upper curve minus lower curve.
Using incorrect intersection limits for leads to a wrong integral. Solve carefully and keep only the first-quadrant intersection for the bounded region with the -axis.
For , mixing integration with respect to and without rewriting the boundaries consistently causes errors. Once you choose , express the horizontal boundaries in terms of and use the correct -limits.
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