the value of summation r=0 to r=m of 10Cr 20Cm-r is maximum when:
  1. 5
  2. 10
  3. 15
  4. 20

Dear student

(1+x)20=C020+C120x+....+C2020x20(1+1/x)10=C010+C110(1/x)+....+C10101/x10given summation= coefficient of xr in (1+1/x)10 ×  coefficient of xm-r in (1+x)20=coefficient of xm in (1+x)20(1+1/x)10=coefficient of xm in (1+x)30x10=coefficient of xm+10 in (1+x)30 =Cm+1030
which is maximum when m=20

Regards

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