Question Details

The area bounded by 0 ≤ y ≤ min{2x,6x − x2 } and x-axis is A. Then 12A is

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Correct Answer :

304

Solution :

The correct answer is 304.

We are given the region bounded by:
0ymin{2x,6x-x2}
and the x-axis (which is y=0).

To find the boundary of the region, we first find the intersection points of the line y=2x and the parabola y=6x-x2 by equating them:
2x=6x-x2
x2-4x=0
x(x-4)=0
So, the curves intersect at x=0 and x=4.

Now, let's analyze the behavior of the two functions for x0:
1. For 0x4, we have 2x6x-x2. Thus, the minimum of the two functions is y=2x.
2. For x4, we have 6x-x22x. Thus, the minimum of the two functions is y=6x-x2.
3. Since we require y0, the boundary curve y=6x-x2 meets the x-axis (y=0) at x=6 (since 6x-x2=0x=6 for x>0).

The graph illustrating this region is shown below:

Therefore, the area A is the sum of two integrals:
A=042x dx+46(6x-x2) dx

Let us compute the first integral:
042x dx=x204=16-0=16

Now let us compute the second integral:
46(6x-x2) dx=3x2-x3346

Evaluating at the upper limit x=6:
3(36)-2163=108-72=36

Evaluating at the lower limit x=4:
3(16)-643=48-643=144-643=803

Subtracting the two values:
36-803=108-803=283

Adding the two parts of the area:
A=16+283=48+283=763

We are required to find 12A:
12A=12×763=4×76=304

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