\(\frac{1981^2-1980^2}{1981^2+1980^2}\)
\(=\frac{\left(1981-1980\right)\left(1981+1980\right)}{1981^2+1980^2}\)
\(>\frac{\left(1981-1980\right)\left(1981+1980\right)}{1981^2+2.1981.1980+1980^2}\)
\(=\frac{\left(1981-1980\right)\left(1981+1980\right)}{\left(1981+1980\right)^2}=\frac{1981-1980}{\left(1981+1980\right)}\)