帮我解两个方程组(1) x/2-x/5=4①x/7-x/15=3②(2) 3(x+y)-4(x-y)=4①x+y/2 + x-y/6 =1 ②quickly 明天要交呀,

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帮我解两个方程组(1) x/2-x/5=4①x/7-x/15=3②(2) 3(x+y)-4(x-y)=4①x+y/2 + x-y/6 =1 ②quickly 明天要交呀,
帮我解两个方程组
(1) x/2-x/5=4①
x/7-x/15=3②
(2) 3(x+y)-4(x-y)=4①
x+y/2 + x-y/6 =1 ②
quickly 明天要交呀,

帮我解两个方程组(1) x/2-x/5=4①x/7-x/15=3②(2) 3(x+y)-4(x-y)=4①x+y/2 + x-y/6 =1 ②quickly 明天要交呀,
⑴、⑴÷3-⑵得:
x/42=-5/3,x=-60;
y=-34/5.
⑵、设(x+y)=a,(x-y)=b,
3a-4b=4 (1)
3a-b=1 ⑵
(1)-(2)得:
b=-1,
a=2/3.
x+y=2/3
x-y=-1
x=-1/6
y=5/6

因为是手机,所以只能发第一题,请见谅
去分母,得5x-2x=40…(3)
15x-7x=1071…(4)
(3)×3,得15x-6x=120…(5)
15x-7x=1071…(6)
(5)-(6),得-x=951
解得x=-951