Question 131558
{{{(a^(-1) - b^(-1))^(-1)}}}
note that {{{a^(-1) = 1/a}}} ,and also {{{b^(-1) = 1/b}}}
{{{((1/a) - (1/b))^(-1)}}}
and, likewise,
{{{((1/a) - (1/b))^(-1) = 1 / ((1/a) - (1/b))}}}
Now multiply the top and bottom by {{{ab}}}
{{{ab / (b - a)}}} answer