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Wait but x = 2 3 ± 5 , and with those values for x , ∣ x + x − 1 ∣ = 2 . 2 3 6 . . . .
I got this by doing the following:
Subsitution - Let y = x 2 .
The equation then becomes:
y + y 1 = 3
→ y 2 − 3 y + 1 = 0
→ y = 2 3 ± 5
Replacing the substitution made at the beginning:
x = y = 2 3 ± 5
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Hm, I'm trying to see what could account for the differences...Wolfram Alpha is not on my side it seems, but I don't see the error in mine. @Calvin Lin could you help? Also, the last line should be plus or minus, Milly.
There were 47 "solvers" out of 48 attempters... that would mean a lot of people got it wrong...
EDIT: Wolfram now likes me? lol here is what i got for the 4 solutions and here is me plugging in a value for x. @Milly Choochoo I see that in your first line you did x + x − 1 , but the + should be a -.
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Oh I guess my comment didn't post properly. After that comment, I posted the following:
GAAAAAAAAAAAAAAAAAAAARGGGGHHH IT WAS A - NOT A + !
CURSE YOU BAD READING SKILLS!
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@Milly Choochoo – Lol it's fine, it taught me to check my problems' solutions before posting :)
the easiest way is=>
make x^2+x^-2 -2=1; i.e.(x-1/x)^2=1 i.e. x-1/x=1;
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The goal is to get the exponents of 2 and -2 into 1 and -1. A feasible way is to use identities relating to sums and differences of squares. Since the answer asks for ∣ x − x 1 ∣ , it could be nice to use ( a − b ) 2 = a 2 − 2 a b + b 2 . Plugging in x for a and x 1 for b , we get ( x − x 1 ) 2 = x 2 − 2 + x 2 1 . This works out nicely because we have two of the terms stated in the original equation and a constant. Now we can rewrite that equation substituting in our previous work: ( x − x 1 ) 2 + 2 = 3 , so ( x − x 1 ) 2 = 1 . Taking the square root gives x − x 1 = ± 1 , so ∣ x − x − 1 ∣ = 1 .