+2 votes
in JEE by kratos

For which of the following values of m, is the area of the region bounded by the curve y = x - x2 and the line y = mx equals 9/2?

(a) -4

(b) -2

(c) 2

(d) 4

1 Answer

+2 votes
by kratos
 
Best answer

Correct option: (b) -2, (d) 4

Case I : When m = 0

In this case y = x - x2 .....(i)

and y = 0 .....(ii)

are two given curves, y > 0 is total region above x-axis.

Therefore, area between y = x - x2 and y = 0 is area between y = x - x2 and above the x-axis

Hence, no solution exists.

Case II: When m < 0

In this case area between

y = x - x2 and y = mx is

OABCO and points of intersection are (0,0) and {1 - m,m(1 - m)}

Case III: When m > 0

In this case y = mx and y = x - x2 intersect in (0,0) and {(1 - m), m(1 - m)} as shown in Fig.

=> (1- m)3 = - 27

=> (1 - m) = - 3

=> m = 3 + 1 = 4.

Therefore, (b) and (d) are the answers.

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