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

Solution :

The correct answer is 17/3.

We are given the set of points (x,y) defining the region S in the first quadrant (x0,y0) satisfying three key boundary conditions:

1. y24xxy24
2. y212-2xx6-y22
3. 3y+8x582x+32y10x5-3y22

Step 1: Finding points of intersection

Let us find the point of intersection of the parabola x=y24 and the line x=5-3y22:

y24=5-3y22

Multiplying by 4:

y2+32y-20=0

Factoring the quadratic equation:

(y-22)(y+52)=0

Since y0, we get y=22, which gives x=(22)24=2.

Similarly, checking the point of intersection between the two parabolas y2=4x and y2=12-2x:

4x=12-2x6x=12x=2,y=22

Notice that the line x=5-3y22 lies strictly inside the region bounded by x=6-y22 for y[0,22]. Thus, the upper bound on x for a given y is dictated by the line.

Step 2: Setting up the Area Integral

For y ranging from 0 to 22, x varies from the left curve xleft=y24 to the right boundary xright=5-3y22.

The total area of region S is given by:

Area=0225-3y22-y24dy

Step 3: Evaluating the Integral

Integrating term-by-term:

Area=5y-3y242-y312022

Substituting the upper limit y=22:

5(22)=102
3(22)242=3×842=62=32
(22)312=16212=432

Subtracting these values:

Area=102-32-432

Area=72-432=7-432=1732

Given that the area of the region is α2, by comparing both expressions, we find:

α=173

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