This is a Rational Expression

Add: 2/x+1 + 1/x-1

\frac{2}{x+1}+\frac{1}{x-1}

You need to get the denominators the same, you can do this by multiplying either term by 1 (anything with the same numerator and denominator):

\frac{2(x-1)}{(x+1)(x-1)}+\frac{1(x+1)}{(x+1)(x-1)}

Can you take it from here?

You need a common denominator. Determine the LCD for x + 1 and x - 1. Multiply each of the original numerators by the missing factor in the original denominator. Then combine the terms in the numerator.