Answer:
k = ab/ ( a^2 - b^2)
Explanation:
a/b=b/a+1/k
Multiply each side by abk to get rid of the fractions
abk *a/b=abk(b/a+1/k)
a^2k = b^2k + ab
Subtract b^2k from each side
a^2k - b^2k = b^2k - b^2k + ab
a^2 k - b^2 k = ab
Factor out k
k( a^2 - b^2) = ab
Divide each side by ( a^2 - b^2)
k( a^2 - b^2)/ ( a^2 - b^2) = ab/ ( a^2 - b^2)
k = ab/ ( a^2 - b^2)