如果x-2y=7,xy=3,则2xy-4y+2x+5

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如果x-2y=7,xy=3,则2xy-4y+2x+5
如果x-2y=7,xy=3,则2xy-4y+2x+5

如果x-2y=7,xy=3,则2xy-4y+2x+5
2xy-4y+2x+5
=2xy+2(x-2y)+5
=2×3+2×7+5
=6+14+5
=25

2*3+2*7+5=25

2xy－4y＋2x＋5
=2xy＋2x－4y＋5
=2xy＋2(x－2y)＋5
=2×3＋2×7＋5
=6＋14＋5
=25

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