Area under the curveHard

Question

For which of the following values of m, is the area of the region bonuded by the curve y = x - x2 and the line y = mx equals

Options

A.-4
B.-2
C.2
D.4

Solution

Case I : When m = 0
In this case       y = x - x2       .....(i)
and       y = 0
are two given curves, y > 0 is total region above x-axis.
Therefore, area between y = x - x2 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 point of intersection are (0, 0) and
{1- m,m(1- m)}
∴     Area of curveOABCO
       
   
   
          (given)
⇒    (1 - m)3 = 27
⇒     1 - m = 3
⇒     m = - 2
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.
       
Area of shaded region =
   
   
   
⇒    &n

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