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Difficult question. Find the value of\[\sqrt{1\sqrt{\frac{17}{16}\sqrt{1\sqrt{\frac{17}{16}\sqrt{1\cdots}}}}}\]
 one year ago
 one year ago
Difficult question. Find the value of\[\sqrt{1\sqrt{\frac{17}{16}\sqrt{1\sqrt{\frac{17}{16}\sqrt{1\cdots}}}}}\]
 one year ago
 one year ago

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badreferencesBest ResponseYou've already chosen the best response.0
@KingGeorge @UnkleRhaukus @TuringTest @Zarkon @bahrom7893
 one year ago

badreferencesBest ResponseYou've already chosen the best response.0
I have the solution, by the way. This is like a challenge. :)
 one year ago

hartnnBest ResponseYou've already chosen the best response.2
y^2 = 1sqrt{17/16y} (y^21)^2 = 17/16y solve...
 one year ago

badreferencesBest ResponseYou've already chosen the best response.0
But \(y\) has one definite value as bounded by the equation before taking the square of both sides. So, which one is it?
 one year ago

badreferencesBest ResponseYou've already chosen the best response.0
That's a good heuristic guess. It's correct. Why?
 one year ago

UnkleRhaukusBest ResponseYou've already chosen the best response.0
\[x=\sqrt{1\sqrt{\frac{17}{16}\sqrt{1\sqrt{\frac{17}{16}\sqrt{1\cdots}}}}}\] \[1x^2={\sqrt{\frac{17}{16}\sqrt{1\sqrt{\frac{17}{16}\sqrt{1\cdots}}}}}\] \[\left((1x^2)^2\frac{17}{16}\right)^2={{\sqrt{1\sqrt{\frac{17}{16}\sqrt{1\cdots}}}}}\] \[\left((1x^2)^2\frac{17}{16}\right)^2=x\]
 one year ago

UnkleRhaukusBest ResponseYou've already chosen the best response.0
am i on the right track?
 one year ago

badreferencesBest ResponseYou've already chosen the best response.0
A polynomial equation that doesn't rigorously determine which of the \(x\)'s are correct. But yes, you and @hartnn are on the right track. From here it's about iteration behavior at certain values.
 one year ago

UnkleRhaukusBest ResponseYou've already chosen the best response.0
i think i accidentally dropped a negative sign
 one year ago

badreferencesBest ResponseYou've already chosen the best response.0
Yes, you did. Haha, I didn't notice. I just saw the polynomials and went, "k"
 one year ago

badreferencesBest ResponseYou've already chosen the best response.0
Not that it makes a difference. A mild algebraic rearrangement leads to the same problem.
 one year ago

UnkleRhaukusBest ResponseYou've already chosen the best response.0
\[\left(\frac{17}{16}(1x^2)^2\right)^2=x\]\[\left(\frac{1}{16}+2x^2x^4\right)^2=x\]\[\frac1{16^2}+\frac{x^2}4\frac{31x^4}{8}4x^6+x^8=x\]\[\frac1{256}x+\frac{x^2}4\frac{31x^4}{8}4x^6+x^8=0\]
 one year ago

badreferencesBest ResponseYou've already chosen the best response.0
Ahaha, that's some unnecessary complexity, but ostensibly it seems right. The difficulty is in showing which one of the \(x\)'s it is, as bounded by the one value \(x\) in the original equation.
 one year ago

sauravshakyaBest ResponseYou've already chosen the best response.1
cant we just substitute the value in y^2 = 1sqrt{17/16y} and see if it is TRUE OR NOT.
 one year ago

sauravshakyaBest ResponseYou've already chosen the best response.1
As squaring gives some unnecessary roots.
 one year ago

UnkleRhaukusBest ResponseYou've already chosen the best response.0
\[1256x+64{x^2}992x^41024x^6+256x^8=0\] \[12^8x+2^6{x^2}31\times2^5x^42^{10}x^6+2^8x^8=0\] \[12^8x+2^4{(2x)^2}62\times(2x)^42^{4}(2x)^6+(2x)^8=0\]
 one year ago

sauravshakyaBest ResponseYou've already chosen the best response.1
dw:1349505055344:dw
 one year ago

sauravshakyaBest ResponseYou've already chosen the best response.1
Only 1/2 satisfies that loop
 one year ago

badreferencesBest ResponseYou've already chosen the best response.0
That's correct, and answers the question, but I feel like I'm missing a technical detail here.
 one year ago

sauravshakyaBest ResponseYou've already chosen the best response.1
dw:1349505240174:dw
 one year ago

badreferencesBest ResponseYou've already chosen the best response.0
Hmm, you used the same solution as I did, but for some reason my solution was corrected to include rates of change around \(x=0.5\). Haha, I'm still trying to catch why.
 one year ago

badreferencesBest ResponseYou've already chosen the best response.0
I think the idea is that asserting\[y=\sqrt{1\sqrt{\frac{17}{16}y}}\]assumes that \(y\) has the innermost radical as \(1\), and iteratively doing this will result in a technical approximation. So we had to determine that the values converge around \(x=0.5\) using straightforward slopes.
 one year ago

badreferencesBest ResponseYou've already chosen the best response.0
But whatever, if there was subtlety here, I'm still missing it. You got the answer.
 one year ago

UnkleRhaukusBest ResponseYou've already chosen the best response.0
\[y=\sqrt{1\sqrt{\frac{17}{16}y}}\]\[1y^2=\sqrt{\frac{17}{16}y}\]\[(1y^2)^2={\frac{17}{16}y}\]\[y+(1y^2)^2{\frac{17}{16}}=0\]\[y+(12y^2+y^4){\frac{17}{16}}=0\]\[y2y^2+y^4{\frac{1}{16}}=0\]\[16y32y^216y^41=0\]\[2^3(2y)2^3(2y)^2(2y)^41=0\]
 one year ago

UnkleRhaukusBest ResponseYou've already chosen the best response.0
\[2^3(2y)2^3(2y)^2(2y)^4(2y)^0=0\]
 one year ago
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