Use Binomial Theorem simply ,
So rth term in the given binomial expansion will be :
(-1)^{r }. ^{n}C_{r} (x^{2})^{n}^{-r }(1/x)^{r} ; here n = 100
==> (-1)^{r} . ^{n}C_{r }x^{200 - 3r} = x^{198}
But equating 200 - 3r and 198 we get r = 2 / 3 which is not an integral value..
But we require that r be an integer as it is used in binomial coefficient ^{n}C_{r}..
Hence there is no term containing x^{198}..
So coefficient of x^{198} in the given binomial expansion = 0