Q32 / 60 · JEE Advanced 2015 (Paper 2) · Mathematics

Let f′x= 192x32+sin4⁡πx for all x∈ R with f12=0.  If m ≤ ∫121fxdx ≤M, then the possible values of m and M are

  • A
    m=13, M=24
  • B
    m=14, M=12  
  • C
    m= -11, M=0
  • Correct answer
    D
    m=1, M=12

Solution

Assuming f(x) to more increasing or less increasing
192x33<f′x<192x32
64x3<f′x<96x3
∫64x3 dx< ∫f′xdx<∫96x3dx

Figure
16x4-1<fx<24x4-32
∫12116x4-1dx<∫121fxdx< ∫12124x4-32dx
2610<∫121fxdx<7820
Hence option m=1, M= 12 is correct.

Hence, the correct answer is option: 'D'.

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