Are you smarter than me? 38

Algebra Level 3

If the largest root of this equation can be expressed as m n \dfrac{m}{n} .Find m + n m+n

( x 3 ) ( x 4 ) (x-3)(x-4) = 34 1089 \dfrac{34}{1089}


The answer is 166.

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4 solutions

Jaiveer Shekhawat
Dec 24, 2014

did it the same way (sometimes laziness can create really good solutions.) :P

sakshi taparia - 6 years, 4 months ago

Why is it if we use (2,17) it would not be integer??? please explain

Dale Angelo Cortez - 6 years ago

this is gold

Razor M - 2 years, 6 months ago
Chew-Seong Cheong
Dec 24, 2014

Let ( x 3 ) ( x 4 ) = 34 1089 x 2 7 x + 12 34 1089 = 0 (x-3)(x-4)=\dfrac {34}{1089}\quad \Rightarrow x^2 - 7x + 12 - \dfrac {34}{1089} = 0

Therefore, the larger root of the equation is:

7 + 7 2 4 ( 12 34 3 3 2 ) 2 = 7 2 + 49 ( 3 3 2 ) 48 ( 3 3 2 ) + 4 ( 33 + 1 ) 66 \dfrac {7 + \sqrt{7^2 - 4\left( 12 - \dfrac {34}{33^2}\right)} } {2} = \dfrac {7}{2} + \dfrac {\sqrt{49(33^2) - 48(33^2) + 4(33+1)} }{66}

= 7 2 + 3 3 2 + 4 ( 33 ) + 4 66 = 7 2 + ( 33 + 2 ) 2 66 = \dfrac {7}{2} + \dfrac {\sqrt{33^2 + 4(33) +4}}{66} = \dfrac {7}{2} + \dfrac {\sqrt{(33+2)^2}}{66}

= 7 2 + 35 66 = 231 + 35 66 = 266 66 = 133 33 = m n = \dfrac {7}{2} + \dfrac {35}{66} = \dfrac {231 + 35} {66} = \dfrac {266} {66} = \dfrac {133} {33} = \dfrac {m}{n}

m = 133 \Rightarrow m = 133 and n = 33 m + n = 166 n = 33\quad \Rightarrow m+n = \boxed{166}

I too did the same But I assumed 33 33 As a a

Mehul Chaturvedi - 6 years, 5 months ago

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@Mehul Chaturvedi is there another way of solving this, because by the use of the quadratic equation anyone can get it, why is this level 4 problem?

Mardokay Mosazghi - 6 years, 4 months ago

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I'm a little confused here. Why are the roots not 19/33 and 28/33 from a straight forward quadratic solution?

Olawale Olayemi - 6 years, 3 months ago
Avn Bha
Dec 25, 2014

assume (x-3)=m therefore m(m-1)=34/33^2

solving quadratic by splitting the middle term

m^2-m-34/33^2=0 =(m-34/33)(m+1/33)

further solving we get x=133/33=166

yup, I too did it the same way. Actually this type of problems one can find in class 10's K.C.Nag book

Raushan Sharma - 6 years, 2 months ago

( x 3 ) ( x 4 ) = 34 1089 x 2 7 x 12 34 1089 = 0 x = 7 + 49 4 ( 12 34 1089 ) 2 x = 7 + 1 + 4 34 1089 2 = 7 + 1225 1089 2 x = 7 + 35 33 2 x = 8 + 2 33 2 x = 4 + 1 33 = 133 33 = m n m + n = 166 (x-3)(x-4)=\dfrac{34}{1089}~~~~~~~~\implies~x^2-7x-12-\dfrac{34}{1089}=0\\ x = \dfrac{7 +\sqrt{49 - 4*(12- \dfrac{34}{1089} )} }{2} \\ x= \dfrac{7 +\sqrt{1 +4* \dfrac{34}{1089} } }{2}=\dfrac{7 +\sqrt{ \dfrac{1225}{1089} } }{2}\\x=\dfrac{ 7 + \dfrac{35}{33} }{2}\\x=\dfrac{ 8 + \dfrac{2}{33} }{2}~~~~ ~~~~~~x=4+\dfrac{1}{33}=\dfrac{133}{33} =\dfrac{m}{n} \\ \therefore~m+n= \boxed {166 }

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