Q35 / 90 · JEE Main 2022 (29 Jul Shift 2) · Mathematics

If t denotes the greatest integer ≤t, then the value of ∫012x-3x2-5x+2+1dx is

  • Correct answer
    A
    37+13-46
  • B
    37-13-46
  • C
    -37-13+46
  • D
    -37+13+46

Solution

I=∫012x-3x2-3x-2x+2+1dx

I=∫012x-3x-2x-1dx+∫011dx

I=∫0232x-3x2-5x+2dx+∫2312x+3x2-5x+2dx+1

I=∫023-3x2+7x-2dx+∫2313x2-3x+2dx+1

Let I1=∫023-3x2+7x-2dx

The graph of y=-3x2+7x-2 and 

I2=∫2313x2-3x+2dx

Figure

So I1=∫0α-2dx+∫α13-1dx+∫1/3β0dx+∫β231·dx

=-2α-13-α+23-β=-α-β+13

y=3x2-3x+2

Figure

When x∈23,1

3x2-3x+2∈43,2

3x2-3x+2=1

∴ I2=∫2313x2-3x+2dx=11-23=13

Hence I=13-(α+β)+13+1

=53-7-376+7-136

=-23+37+136=-23+37+136

=37+13-46

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

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