Let m be the largest real solution to the equation x − 3 3 + x − 5 5 + x − 1 7 1 7 + x − 1 9 1 9 = x 2 − 1 1 x − 4 .
There are positive integers a , b , c such that m = a + b + c . Find a + b + c .
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Mathematics is an art of deceiving. I did by twice substitution, first substitute x − 3 = a and x − 1 7 = b , yielding that a − 2 = x − 5 and b − 2 = x − 1 9 to make it easier. Solving as usual until reaching a b − a − b form, then substitute into y and completeing square. Returning to x and complete square.
I, still, love this deceiving problem
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Probably substituting from the start a=x - 11,might be better. (x-3)=a+8, (x-8) =a - 8.,,,,.(x-5)=a+6, (x-17)=a - 6. .........This would simplify Aareyan Manzoor's first stage.
Just wondering what is a,b and c as it didn't mention more...
Great!! Good solution too....
really nice solution but same approach...
For those interested, this was Problem 14 AIME I 2014
Same solution
Very well done! Did you get any hint from friend?
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nope, sir. i remember solving this and applied a similar method.
Enjoyed solving it......
Same pinch :)
All most the same approach. Only used Y = X 2 − 2 2 X + 7 1 . S o ( X − 3 ) ( X − 1 9 ) = Y − 1 4 , a n d ( X − 5 ) ( X − 1 7 ) = Y + 1 4 . E q u a t i o n t u r n s t o b e Y 2 − 4 Y − 1 4 2 = 0 Solving we get Y. Substituting for Y, and solving for X we get the answer.
You wrote it perfectly. Thumbs up!
Did the same way.
General method should expand b l i n d l y but not too difficult with Excel. { A B r u t e F o r c e A p p r o a c h ! }
x 5 − 5 5 x 4 + 1 1 0 6 x 3 − 9 8 7 8 x 2 + 3 7 9 5 7 x − 5 0 1 7 1 = 0 {An x = 0 was eliminated.}
Figures of Excel correlated with other 18 S.F. solver:
α = 11.00000000000000
β = 19.13278154285057
γ = 17.15287448078287
δ = 4.847125519217132
ϵ = 2.867218457149427
All checked to be correct to very close's proximity.
Numerical method can achieve a merit easily for 19.13278154285057 → 1 1 + 5 2 + 2 0 0 .
11 + 52 + 200 = 263
Answer: 2 6 3
Lu, to save your trouble. Just use Wolfram Alpha ( see here )but computer solution is unneeded here. Click More roots under Solutions.
Very easy and fast one gets the solution via Xmaxima:
solve(x^2-11*x-4-3/(x-3)-5/(x-5)-17/(x-17)-19/(x-19),x);
7/2 7/2
sqrt(208 - 5 2 ) sqrt(208 - 5 2 )
[x = 11 - ------------------, x = ------------------ + 11,
2 2
7/2 7/2
sqrt(5 2 + 208) sqrt(5 2 + 208)
x = 11 - ------------------, x = ------------------ + 11, x = 11, x = 0]
2 2
As third last value of the solutions' list you find the largest real solution (x=19.13278...) and after some equivalent transformation you have x = 1 1 + 5 2 + 2 0 0 .
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first off.. i loved this problem, thanks to the creator for giving me such great experience. start like this x − 3 3 + x − 5 5 + x − 1 7 1 7 + x − 1 9 1 9 + 4 = x 2 − 1 1 x x − 3 3 + 1 + x − 5 5 + 1 + x − 1 7 1 7 + 1 + x − 1 9 1 9 + 1 = x 2 − 1 1 x x − 3 x + x − 5 x + x − 1 7 x + x − 1 9 x = x ( x − 1 1 ) we get x=0 as a solution. now divide by x and put x=y+11 y + 8 1 + y − 8 1 + y + 6 1 + y − 6 1 = y y 2 − 6 4 2 y + y 2 − 3 6 2 y = y y=0 ->x=11 is another solution. we divide again to get y 2 − 6 4 2 + y 2 − 3 6 2 = 1 2 ( y 2 − 3 6 ) + 2 ( y 2 − 6 4 ) = ( y 2 − 6 4 ) ( y 2 − 3 6 ) 4 y 2 − 2 0 0 = y 4 − 1 0 0 y 2 + 2 3 0 4 y 4 − 1 0 4 y 2 + 2 5 0 4 = 0 y 2 = 5 2 ± 2 0 0 y = ± 5 2 ± 2 0 0 x = 1 1 ± 5 2 ± 2 0 0 we get that x = 0 , 1 1 , 1 1 ± 5 2 ± 2 0 0 the required x l a r g e s t = 1 1 + 5 2 + 2 0 0 1 1 + 5 2 + 2 0 0 = 2 6 3