On higher order infinitesimals o(x^2)+o(x^2)=?

On higher order infinitesimals o(x^2)+o(x^2)=?

From the definition, we know limx - > 0 o (x ^ 2) / x ^ 2 = 0
limx->0 [o(x^2)+o(x^2)]/x^2=limx->0 o(x^2)/x^2+limx->0 o(x^2)/x^2=0+0=0
o(x^2)+o(x^2)=o(x^2)