Having already informed us, regarding all the miracles, that Moshe and Aharon worked together to perform them, why does the Torah need to repeat it here?
Rashi: This is actually an introduction to the following paragraph (Shemos 12:1-20), where Hashem will instruct Moshe and Aharon to teach Yisrael about the Korban Pesach. 1
Ramban: Moshe and Aharon's participation in the Makos has now come to an end (seeing as they will take no part in Makas Bechoros), and they have also warned Pharaoh about Makas Bechoros. Consequently, the Torah is now telling us that they did everything that Hashem asked of them to the letter.
Seforno: The current three Pesukim (11:9-10 and 12:1) go together: Hashem has just informed Moshe that He hardened Pharaoh's heart in order to increase His wonders, so that both the Egyptians and Yisrael would learn Hashem's greatness and goodness from them (See earlier 10:2), Moreover, it was to this end that Moshe and Aharon worked together to perform all the miracles up until now. Consequently, now that Hashem is about to punish the Egyptians and save Yisrael (some of whom deserved to be included in the punishment) and to destroy the gods of Egypt - by means of the Korban Pesach, 2 He wanted this too, to be done via Moshe and Aharon together (just as together, they had tried to bring the Egyptians to do Teshuvah, and to guide Yisrael, so that together, they would merit to take Yisrael out of Egypt, to enjoy the fruits of their labor).
