"אנחנו חייבים ללמוד הרבה נוסחאות."

Translation: We must learn lots of formulae.

[esdrujula69]

<3 DuoLingo for using formulae. Complaining about this would be like complaining if Duo's answers were phrased like "the bank in which i keep my money" and not "the bank i keep my money in". Nothing wrong with teaching people a slightly more formal and technically correct form

[TeribleT]

Anachnu chayavim lilmod harbe nuscha'ot¹

¹ Can someone confirm if this is correct? Thank you in advance!

[Hadassah277241]

Formulae? Seriously? (And Duo marks me wrong for using Hebrew that is perfectly correct but not commonly used...)

[gsazbon]

Is not חייב an obligation, requirement and not a need?