Q.

If 26(233(C212)+255(C412)+277(C612)+...+21313(C1212))=313–α, then α is equal to:          [2026]

1 45  
2 48  
3 51  
4 54  

Ans.

(3)

26[233(C212)+255(C412)+277(C612)+...+21313(C1212)]=313–α

=2[23·C313+25·C513+27·C713+...+213·C1313]

=2[(1+2)13–(1–2)132–26]

=313+1–52=313–51      ∴ α=51