Question Details

Let  S = { ( x , y ) R × R : x 0 , y 0 , y 2 4 x , y 2 12 2 x  and 3 y + 8 x 5 8 } . If the area of the region S is α√2, then α is equal to

Options

A

17/2

B

17/3

C

17/4

D

17/5

Show Answer

Correct Answer :

Option B

17/3

17/3

Solution :

To find the area of the region S, we first analyze the given boundaries:
1. x0 and y0 (which restricts the region to the first quadrant).
2. y24xxy24
3. y212-2xx6-y22
4. 3y+8x58x5-38y

First, let us find the intersection points of these curves:
For the two parabolas, x=y24 and x=6-y22:
y24=6-y22
Multiplying by 4:
y2=24-2y23y2=24y2=8
Since y0, we have y=8=22.
Substituting y=8 into x=y24 gives:
x=84=2
So, the intersection point of the two parabolas is (2,8).

Now, let us check where the boundary line 3y+8x=58 passes.
If we substitute y=8 and x=2 into the equation:
3(8)+8(2)=58
This satisfies the equation, showing that all three boundary curves intersect at the single point (2,8).

Let us determine the bounds of x in terms of y for the region S:
For 0y8, we have:
y24x5-38y
Therefore, the area A of the region S is given by the integral:
A=085-38y-y24dy

Integrating term by term:
A=5y-328y2-y31208

Evaluating this at the upper limit y=8:
1. First term: 58=102
2. Second term: -328(8)=-128=-1222=-32
3. Third term: -(8)312=-8812=-23(22)=-432

Combining the terms:
A=102-32-432
A=72-432
A=7-432=1732

Given that the area of region S is α2, we compare it with our result:
α2=1732α=173

Thus, the correct option is 17/3.

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