Answer
$ \log_{a}(x^{3}+y^{3}) $
Work Step by Step
Applying the rule: $\log_{a}(MN)=\log_{a}M+\log_{a}N,$
$\log_{a}(x+y)+\log_{a}(x^{2}-xy+y^{2})=\log_{a}[(x+y)(x^{2}-xy+y^{2})]$
...we have a sum of cubes in the brackets...
$=\log_{a}(x^{3}+y^{3}) $
