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JEE Main201911 Jan 2019Morning ShiftMathematicsBinomial TheoremActual

The value of r for which 20 r 20 0 + 20 r-1 20 1 + 20 r-2 20 2 + + 20 0 20 r is maximum, is:

Options

  1. A15
  2. B20
  3. C11
  4. D10

Correct answer

B. 20

Step-by-step solution

Consider the expression 20 r 20 0 + 20 r-1 20 1 + 20 r-2 20 2 + + 20 0 20 r For maximum value of above expression r should be equal to 20 . as array l 20 20 20 0 + 20 19 20 1 + + 20 20 20 0 = ( 20 0 )²+ ( 20 1 )²+ + ( 20 20 )²= 40 20 array Which is the maximum value of the expression, So, r=20 .

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