Algebra: A Combined Approach (4th Edition)

$\dfrac{-9}{25x^{2}-1}+\dfrac{7}{1-25x^{2}}=-\dfrac{16}{25x^{2}-1}$
$\dfrac{-9}{25x^{2}-1}+\dfrac{7}{1-25x^{2}}$ Change the sign of the numerator and the denominator of the second fraction: $\dfrac{-9}{25x^{2}-1}+\dfrac{7}{1-25x^{2}}=\dfrac{-9}{25x^{2}-1}+\dfrac{-7}{25x^{2}-1}=...$ Now we have to rational expressions with the same denominator, evaluate the sum by adding the numerators and using the same denominator. After that, simplify if possible: $...=\dfrac{-9-7}{25x^{2}-1}=-\dfrac{16}{25x^{2}-1}$