题目内容
解方程组或不等式(组) (每题6分共30分)
(2)
(3)
(1)
(4)
(5)
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(1)
(4)
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(1)
(2)
(3)
(4)
(5)不等式组无解

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(1)①
2+②得5x=15
解得x=3
代入①得3+y=3
解得y=0
所以方程组的解为
(2)②去分母整理得-4x+6y=-13
与①相加得3y=-6
解得y=-2
代入①得x=
所以方程组的解为
(3)①-②得x-z=-1
与③相加得2x=2
解得x=1
代入①得y=0
代入③得z=2
所以方程组的解为
(4)去括号整理得-6x<-28
解得x>
(5)解①得x<
,解②得x>
所以不等式组无解

解得x=3
代入①得3+y=3
解得y=0
所以方程组的解为

(2)②去分母整理得-4x+6y=-13
与①相加得3y=-6
解得y=-2
代入①得x=

所以方程组的解为

(3)①-②得x-z=-1
与③相加得2x=2
解得x=1
代入①得y=0
代入③得z=2
所以方程组的解为

(4)去括号整理得-6x<-28
解得x>

(5)解①得x<


所以不等式组无解

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