4 boys and 2 girls occupy seats in a row at random. Then the probability that the two girls occupy seats side by side is
A coin is tossed again and again. If tail appears on first three tosses, then the chance that head appears on fourth toss is
If A and B are coefficients of xn in the expansions of (1 + x)2n and (1+ x)2n - 1 respectively, then A /B is equal to
4
2
9
6
If n > 1 is an integer and x 0, then (1 + x)n - nx - 1 is divisible by
nx3
n3x
x
nx
C.
x
Hence, it is divisible by x.