Which is true about the degree of the sum and difference of the polynomials 3x5y – 2x3y4 – 7xy3 and –8x5y + 2x3y4 + xy3?

The degree of a term is the sum of its variable exponents. In the sum, the x³y⁴ terms cancel, leaving terms of degrees 6 (x⁵y) and 4 (xy³), so the sum has degree 6. In the difference, the x³y⁴ terms combine to a nonzero term, and its degree is 3 + 4 = 7; therefore, the difference has degree 7. Choice C is correct.

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