Explanation:
For the expression (s-t)(s/t) we first use the distributive property:
\((s-t)(\frac{s}{t})
\\
\\=s\times \frac{s}{t}-t\times \frac{s}{t}\)
We can write both s and t as fractions by using a denominator of 1:
\(\\=\frac{s}{1}\times \frac{s}{t}-\frac{t}{1}\times \frac{s}{t}\)
To multiply frations, we multiply straight across:
\(=\frac{s\times s}{1\times t}-\frac{t\times s}{1\times t}
\\
\\=\frac{s^2}{t}-\frac{ts}{t}\)
In the second fraction, st/t, the t will divide out, or cancel, since it is in both the numerator and denominator:
\(\frac{s^2}{t}-s\)
