若3x-y=7 则 -6x+2y-3=..,.,.,.,.,.,.,.,.,.,.,tongshang

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若3x-y=7则-6x+2y-3=..,.,.,.,.,.,.,.,.,.,.,tongshang若3x-y=7则-6x+2y-3=..,.,.,.,.,.,.,.,.,.,.,tongshang若3

若3x-y=7 则 -6x+2y-3=..,.,.,.,.,.,.,.,.,.,.,tongshang
若3x-y=7 则 -6x+2y-3=
..,.,.,.,.,.,.,.,.,.,.,tongshang

若3x-y=7 则 -6x+2y-3=..,.,.,.,.,.,.,.,.,.,.,tongshang
-(6x-2y)-3
=-2(3x-y)-3
=-2*7-3
=-17

3x-y=7,等式两边同乘以-2,得
-6x+2y=-14
所以-6x+2y-3=-14-3=-17

-6x+2y-3=-2(3x-y)-3=-2×7-3=-17