2 x − 2 y + z 1 2 y − 2 z + x 1 2 z − 2 x + y 1 = = = 2 0 1 4 1 2 0 1 4 1 2 0 1 4 1
Find all positive real numbers x , y , z such that they satisfy the system of equation above. Submit your answer as x + y z − z x .
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Fantastic work!
add all the three equations. you'll end up getting (1/x) + (1/y) + (1/z) = (3/2014) .. let us assume that x=y=z=2014......... and then calculate x+ yz - zx
Any permutation of x,y,z leaves the equations unaffected. If any 2 of x,y,z are different, some permutations will affect the 3 numbers x,y and z. This contradicts the fact that the equations are unaffected. So x=y=z. However, this means that x=y=z=2014.
Just observe that x = y = z = 2 0 1 4 and so get the needed expression.
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if we sum above three equation, we can get
x 1 + y 1 + z 1 = 2 0 1 4 3 .
And If we calculate ( 1 e q u a t i o n ) × z + ( 2 e q u a t i o n ) × x + ( 3 e q u a t i o n ) × y ,
we can also get x + y + z = 3 × 2 0 1 4 .
with 'Arithmetic Mean' ≥ 'Harmonic mean Inequality' ( x 1 + x 2 + x 3 + . . . + x n ) × ( x 1 1 + x 2 1 + x 3 1 + . . . + x n 1 ) ≥ n 2
with equality if and only if x 1 = x 2 = ⋯ = x n .
( x 1 + y 1 + z 1 ) × ( x + y + z ) = 3 2 so x = y = z than x + y z − z x = 2 0 1 4