Question

1/х+1/у=3/8;
{
Х+у=12

Answer 1

1/x+1/y=3/8
x+y=12
------------------------
(x+y)/xy=3/8
x+y=12
--------------------
12/xy=3/8
x+y=12
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8.12=3xy
x+y=12
---------------------
8.4=xy
x+y=12
--------------
xy=32
x+y=12
------------------
xy=32
x=12-y
--------------------
(12-y)y=32
x=12-y
-----------------
12y-y²=32
x=12-y
----------------------
y²-12y+32=0
x=12-y
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y²-12y+32=0, D=144-128=16,√D=√16=4
y1=(12+4)/2=16/2=8
y2=(12-4)/2=8/2=4
x=12-y
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a)y1=8, x1=12-8, x1=4
b)y1=4,x2=12-4=8, x2=8
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Otvet: /x,y/=/4,8/ i /x,y/=/8,4/