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Algebra Level 3

{ x + y + z = 26 1 x + 1 y + 1 z = 31 \begin{cases}{x+y+z=26} \\ {\frac{1}{x}+\frac{1}{y}+\frac{1}{z}=31}\end{cases}

The two equations above satisfy the real numbers x , y , z x,y,z . What is the value of the expression below?

x y + y z + z x + x z + z y + y x \frac{x}{y}+\frac{y}{z}+\frac{z}{x}+\frac{x}{z}+\frac{z}{y}+\frac{y}{x}


The answer is 803.

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4 solutions

Discussions for this problem are now closed

Paola Ramírez
Jan 15, 2015

( x + y + z ) ( 1 x + 1 y + 1 z ) = 26 × 31 (x+y+z)(\frac{1}{x}+\frac{1}{y}+\frac{1}{z})=26\times 31

x y + y z + z x + x z + z y + y x + 3 = 806 \frac{x}{y}+\frac{y}{z}+\frac{z}{x}+\frac{x}{z}+\frac{z}{y}+\frac{y}{x}+3=806

x y + y z + z x + x z + z y + y x = 803 \boxed{\frac{x}{y}+\frac{y}{z}+\frac{z}{x}+\frac{x}{z}+\frac{z}{y}+\frac{y}{x}=803}

wow! I did the same.

Nelson Mandela - 6 years, 4 months ago

I too did in the same way

Sudhir Aripirala - 6 years, 4 months ago

Sometimes a simple idea could solve problems that look difficult:)

For example this as easy as

Paola Ramírez - 6 years, 4 months ago

Really simple!

Luciano Canela - 6 years, 4 months ago

what if we have to find the value of (x+y)xy + (y+z)yz + (x+z)xz @paolaRamieze

Rajdeep Dhingra - 6 years, 4 months ago

x + y = 26 z x+y=26-z

x + z = 26 y x+z=26-y

z + y = 26 x z+y=26-x

You'll get into the same answer...

Roman Frago - 6 years, 4 months ago

i am unable to get its answer. please pst how

Ravi Raj - 6 years, 4 months ago

I did it ur way as well, u just need to break it up into three terms and simplify. U have to do this with the denominator.

Sugam Bhandari - 6 years, 4 months ago

Interesting, I'll solve it

Paola Ramírez - 6 years, 4 months ago
Arman Hemel
Mar 2, 2015

y/x + z/x + x/y + z/y + x/z + y/z ( y + z ) / x + ( x + z ) / y + ( x + y ) / z ( 26 - x ) / x + ( 26 - y ) / y + ( 26 - z ) / z 26/x - x/x + 26/y - y / y + 26 /z - z/z 26/x + 26/y + 26/z - 1 -1 -1 26( 1/x + 1/y + 1/z ) - 3 26 x 31 - 3 806 - 3 803

Anna Anant
Jan 24, 2015

x+y+z=26

1/x + 1/y+ 1/z = 31

x/y+x/z + y/z+y/x + z/x+z/y = k

x( 1/y + 1/z) + y(1/x + 1/z) +z(1/x + 1/y) =k

1/y+ 1/z = 31-1/x 1/x+ 1/z = 31-1/y 1/y+ 1/z = 31-1/z

x( 31-1/x) + y(31-1/y) +z(31-1/z) =k 31x + 31y + 31z -3=k 31(x+y +z) -3=k 31(26) -3=k 803=k

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