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Algebra Level 4

x 2014 2 + x 2010 3 + x 2004 4 + + x 1906 11 = 55 \large \frac{x-2014}2 + \frac{x-2010}3 + \frac{x-2004}4 + \ldots + \frac{x-1906}{11} = 55

Solve for x x .


The answer is 2016.

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2 solutions

Ano Maly
Jul 8, 2015

Note that there are ten terms on the RHS, and that 55 55 is the sum of the first 10 10 natural numbers, not including 0 0 . Thus the first term on the RHS must be equal to 1 1 the second equal to 2 2 , the third equal to 3 3 , etc. Solving for x x in ten first term, we get x = 2016 x = 2016 . Because x x is constant throughout the entire problem, we have just solved for x in the entire problem. So, x = 2016 \boxed{x = 2016}

I would like to thank TheOnly Caosun, who helped me with this problem.

Great problem, @Satyajit Mohanti

Can you explain why "thus the terms must be equal to 1, 2, 3, ..."?

Calvin Lin Staff - 5 years, 11 months ago

Same approach

Aakash Khandelwal - 5 years, 11 months ago
Sriharsha Ch
Apr 15, 2016

On the LHS there are 10 terms and the RHS is 55, which is the sum of the first 10 natural numbers. Thus we can seperate 55 into 1 , 2 , 3 and so on... to make an equation like this. :

x 2014 2 \frac{x - 2014}{2} + x 2010 3 \frac{x-2010}{3} + . . . . . ..... = = 1 + 2 + . . . . . 1 + 2 + .....

If we subtract 1 on the RHS from the first term on the LHS , we will get:

x 2014 2 \frac{x-2014}{2} 1 - 1 = = x 2014 2 2 \frac{x - 2014 - 2}{2} = = x 2016 2 \frac{x - 2016}{2}

Similarly , if we subtract 2 from the second term on the LHS , we will get:

x 2010 3 \frac{x-2010}{3} 2 - 2 = = x 2010 2 3 3 \frac{x - 2010 - 2*3}{3} = = x 2016 3 \frac{x - 2016}{3}

Doing this to all terms, we will get this equation:

x 2016 2 \frac{x - 2016}{2} + + x 2016 3 \frac{x - 2016}{3} + + x 2016 4 \frac{x - 2016}{4} + + . . . . . . . . . . . . ............ = = 0 0

Since the term x 2016 x - 2016 is constant on the LHS , even taking the LCM we will ultimately obtain this equation:

x 2016 = 0 x - 2016 = 0

Thus solving for the equation, we will ultimately obtain:

x = 2016 \boxed{x = 2016}

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