^mC_r+ ^mC_r-1ⁿC₁+^mC_r-2. ⁿC₂+………..+ ⁿC_r =

Sum of the last 20 coefficients in the expansion of (1+x)³⁹, when expanded in ascending powers of x, is

The 4^th term of ⁶(x+2/x²)⁶ is

If x is so small that x² and higher powers of x may be neglected then (1-x)^1/2(1+x)^2/3/(1-x)^1/2

3√1003 -3√997