～はずがない

About

はず ("should/bound to") can be combined with がない to express that the speaker believes something is impossible. ～はずがない is often translated to "there's no way X" or "X is impossible".

～はずがない can also be combined with a negative phrase. In this case, there is a double negative, and ～はずがない flips its meaning to "X must be the case" or "there's no way that X isn't the case".

～はずはない is also possible. は puts more emphasis on ない, and creates a sense of contrast between one thing that the speaker sees as impossible, and one thing that they do not.

Summary

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  ～はずがない means "there's no way X"

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  ～はずがない can form a double negative and flip its meaning by following a negative phrase

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  ～はずはない is also possible