How many terms would the expansion of (a-b) 8 have?

In any binomial expression, the number of terms is always one more than power of the expression.

Examples:

(x+y) ^1 will give 1+1 = 2 terms

(x+y) ^2 will give 2+1 = 3 terms

The given expression is:

(a-b) ^8

The power of the expression is 8 which means that:

number of terms = 8+1 = 9 terms