已知4[1-2(x+y)]+2[-(x+y)-5]=-14(x+y),求3x+3y的值.用一元一次方程解,谢谢...
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已知4[1-2(x+y)]+2[-(x+y)-5]=-14(x+y),求3x+3y的值.用一元一次方程解,谢谢...
已知4[1-2(x+y)]+2[-(x+y)-5]=-14(x+y),求3x+3y的值.用一元一次方程解,谢谢...
已知4[1-2(x+y)]+2[-(x+y)-5]=-14(x+y),求3x+3y的值.用一元一次方程解,谢谢...
设x+y=z
则:4(1-2z)+2(-z-5)=-14z
z=3/2
3x+3y=3z=9/2
4[1-2(x+y)]+2[-(x+y)-5]=-14(x+y)
4-8(x+y)-2(x+y)-10=14(x+y)
4(x+y)=6
x+y=3/2
3x+3y=9/2
用整体思想,设x+y为一个数比如a,那么方程就变为4[1-2a]+2[-a-5]=-14a,解出a得1.5,那么3x+3y就等于3a等于4.5了
化简得:4-8(x+y)-2(x+y)-10=-14(x+y)
移项合并得:4(x+y)=6
故x+y=3/2
3x+3y=9/2