x y z = = = y 2 − 1 6 1 + z 2 − 1 6 1 z 2 − 2 5 1 + x 2 − 2 5 1 x 2 − 3 6 1 + y 2 − 3 6 1
Given that x , y and z are real numbers that satisfy the system of equations above. If x + y + z = n m where m , n are positive integers and n is square-free, find the value of m + n .
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Perfect combination of Geometry and Algebra to solve a Number Theory problem. Nice job thumb-ups .
Very nice problem!
are u really 13???
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Yes!! @Chirag Singapore
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is this the first time you encountered a problem whose solution is related to triangles or you have done it before. And y do you have an IIt Bombay symbol ?
to get the answer follow the steps given below:
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Let △ X Y Z be a triangle with sides of length x , y and z , and suppose this triangle is acute (so all altitudes are on the interior of the triangle). Let the altitude to the side of length x be of length h x , and similarly for y and z . Then we have by two applications of the Pythagorean Theorem that x = y 2 − h x 2 + z 2 − h x 2 . As a function of h x , the RHS of this equation is strictly decreasing, so it takes each value in its range exactly once. Thus we must have that h x 2 = 1 6 1 and so h x = 4 1 and similarly h y = 5 1 and h z = 6 1 Since the area of the triangle must be the same no matter how we measure, x ⋅ h x = y ⋅ h y = z ⋅ h z and so 4 x = 5 y = 6 z = 2 A and x = 8 A , y = 1 0 A and z = 1 2 A . The semiperimeter of the triangle is s = 2 8 A + 1 0 A + 1 2 A = 1 5 A so by Heron's formula we have A = 1 5 A ⋅ 7 A ⋅ 5 A ⋅ 3 A = 1 5 A 2 7 . Thus A = 1 5 7 1 and x + y + z = 3 0 A = 7 2 and the answer is 2 + 7 = 9