1/x+1/y=1/21 3/x+5/y=3/14怎么结出x 和
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1/x+1/y=1/21 3/x+5/y=3/14怎么结出x 和
1/x+1/y=1/21 3/x+5/y=3/14
怎么结出x 和
1/x+1/y=1/21 3/x+5/y=3/14怎么结出x 和
令a=1/x.b=1/y
则a+b=1/21 (1)
3a+5b=3/14 (2)
(1)×5-(2)
5a-3a=5/21-3/14
2a=1/42
a=1/84
b=1/21-a=1/28
所以
x=1/a=84
y=1/b=28
1/x+1/y=1/21 (1)
3/x+5/y=3/14 (2)
(1)×5-(2)得
2/x=1/42
x=21 代人(1)得
y=0
X=1/x,Y=1/y
X+Y=1/21
3X+5Y=3/14
3X+3Y=1/7
3X+5Y=3/14
5Y-3Y=3/14-1/7
2Y=1/14
Y=1/7
y=1/Y=7
X=1/21-Y=1/21-1/7=-2/21
x=1/X=-21/2
将1/x设为m,1/y设为n.
则有 m+n = 1/21
3m+5n=3/14
所以,m=1/21-- n
即,1/7 --3n +5n = 3/14
所以啦,n = 1/28
m = 1/84
设1/x=a,1/y=b
a+b=1/21
3a+5b=3/14
so a=1/84
b=1/28
x=84 y=28
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