Q31 / 54 · JEE Advanced 2017 (Paper 2) · Mathematics

If the line x=α divides the area of the region R={x,y∈R2:x3≤y≤x, 0≤x≤1} into two equal parts, then

  • Correct answer
    A
    12<α<1
  • B
    α4+4α2-1=0
  • C
    0<α≤12
  • Correct answer
    D
    2α4-4α2+1=0

Solution

Figure

A= ∫01x-x3dx=14

Area of curvilinear triangle OPQ=A2=18

⇒     ∫01x-x3dx=18 ⇒  2α4-4α2+1=0

⇒   α2-12=12 ⇒  α2=2-12

so α lies between 0.5 and 1

Hence, the correct answer is options: 'A', 'D'.

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