Given x, y, z in RR, such that 1/x+1/(y+z)=1/2 and 1/y+1/(z+x)=1/3 and 1/z+1/(x+y)=1/4. Find the value of x.

Audrey Mckee

Audrey Mckee

Answered question

2022-09-10

What's the value of x if 1 x + 1 y + z = 1 2 and 1 y + 1 z + x = 1 3 and 1 z + 1 x + y = 1 4 . Find the value of x.

Answer & Explanation

Illuddybopylu

Illuddybopylu

Beginner2022-09-11Added 17 answers

I suggest to go for X = 1 x , Y = 1 y and Z = 1 z because it has the advantage to simplify the denominators.
The equations become
X Y + Y Z + Z X Y + Z = 1 2 ; X Y + Y Z + Z X X + Z = 1 3 ; X Y + Y Z + Z X X + Y = 1 4
And it gives a simple system to solve
{ Y + Z = 2 k X + Z = 3 k X + Y = 4 k X Y + Y Z + Z X = k
For instance ( 2 ) ( 1 ) gives X Y = k and reporting in ( 3 ) gives 2 Y = 3 k.
This is all similar easy calculation and we end up with X = 5 2 k , Y = 3 2 k , Z = 1 2 k and 23 k 2 4 = k
Finally x = 1 X = 2 5 × 23 4 = 23 10 .

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