Why are women required to eat matzah on the night of Seder and say the Haggaddah? Both are mitzvas oseh she’hazman grama… And if the anser is “af hain b’oseh ha’nas” that is only by a mitzvah d’rabbanan and not d’oraisa. What is the answer to this? (besides for the Kehillas Yaakov and what he says.)
The Gemara (43b) explains that women are obligated in matzah because there are obligated in the negative prohibition against chametz: Just as they are obligated in the negative, so in the positive mitzvah of matzah.
The matter of telling Yetzias Mitzrayim is less clear. The Chinuch writes that women are obligated in the mitzvah, but the Minchas Chinuch questions this. Indeed, from the Rambam’s listing of mitzvos that apply to women it appears that they are not obligated.
One explanation why they are obligated is that telling the tale of Yetzias Mitzrayim is related to the mitzvah of matzah, which has to be “bread that many matters are answered upon.” Thus, the mitzvah of “sippur” is included in the obligation of matzah.