x + x 1 = x 2 + x 2 1
If the equation above is true for some real positive value x , what is the value of x 1 0 2 4 + x 1 0 2 4 1 ?
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@Brian Charlesworth Sir, I am thinking about the level.. How about you?
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I'm surprised that, with 54 solvers already, the level hasn't been set yet. It's usually an automatic process, but it can take longer if you don't initially attach a level to the problem when you post it. I would consider this a level 2 problem.
@Brian Charlesworth No problem.. Thx for your suggestion..
@Brian Charlesworth No problem.. Thx for your suggestion.. By the way, i'm still 14..
x + x 1 = x ² + x ² 1
Multiply both side by x ²
x ³ + x = x 4 + 1
x 4 − x ³ − x + 1 = 0
If x = 1 , the equation is complete. Then, we have x = 1 .
Hence,
x 1 0 2 4 + x 1 0 2 4 1 = 1 + 1
= 2
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Since x 2 + x 2 1 = ( x + x 1 ) 2 − 2 , if we let x + x 1 = y the given equation becomes
y = y 2 − 2 ⟹ y 2 − y − 2 = ( y − 2 ) ( y + 1 ) = 0 ,
so either y = 2 or y = − 1 . But as x > 0 we must have y > 0 , and so
y = x + x 1 = 2 ⟹ x 2 + 1 = 2 x ⟹ x 2 − 2 x + 1 = ( x − 1 ) 2 = 0 ⟹ x = 1 .
Thus x 1 0 2 4 + x 1 0 2 4 1 = 1 + 1 1 = 2 .