The value of r for which 20cr 20c0+ 20cr−120c1+20cr−220c2+…20c020cr is maximum, is
The value of r for which 20cr 20c0+ 20cr−120c1+20cr−220c2+…20c020cr is maximum, is
Given sum=coefficient of xr in the expansion of (1+x)20 (1+x)20, which is equal to 40cr It is maximum when r=20