合并同类项.要写清楚.5yx－3x²y－7xy²＋6xy－12xy＋7xy²＋8x²y

合并同类项.要写清楚.5yx－3x²y－7xy²＋6xy－12xy＋7xy²＋8x²y
合并同类项.要写清楚.
5yx－3x²y－7xy²＋6xy－12xy＋7xy²＋8x²y

合并同类项.要写清楚.5yx－3x²y－7xy²＋6xy－12xy＋7xy²＋8x²y
5yx－3x²y－7xy²＋6xy－12xy＋7xy²＋8x²y
=(5+6-12)xy+(-3+8)x²y+(-7+7)xy²
=-xy+5x²y

5yx－3x²y－7xy²＋6xy－12xy＋7xy²＋8x²y
＝﹙5xy＋6xy－12xy﹚＋﹙8x²y－3x²y﹚＋﹙7x²y－7x²y﹚
＝﹣xy＋5x²y.