1 answer
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= 5x^3 - 2x^4 + 4x^4 - 5x^3
= -2x^4 + 4x^4 + 5x^3 - 5x^3
= 2x^4
= -2x^4 + 4x^4 + 5x^3 - 5x^3
= 2x^4