还是合并同类项2x2次方+1-3x+7-3x2次方+5x

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原式=(2-3)x²+(-3+5)x+(1+7)
=-x²+2x+8

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2x²?1-3x+7-3x²+5x
=2x²-3x²没喊+5x-3x?1+7
=?2-3?x²+?5-3?x?1+7
=?x²御陪+2x?枯拆野8

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