Let , and be the sides of a traingle. Then let the perimeter of the triangle be , let the area of the triangle divided by the square root of the perimeter be , let the magnitude of side and let the semi perimeter minus the magnitude of side be the smallest root of the polynomial . Then, if the magnitude of side can be expressed as , the magnitude of side can be expressed as and the magnitude of side can be expressed as , find and . Submit your answer as the sum of the digit sums of and , where the digit sum includes the digits both sides of the decimal point (for example, the digit sum of is ).
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By the Rational Root Theorem , if the roots of the polynomial x 3 − 9 x 2 + 2 6 x − 2 4 are rational, they'll be in the set ( ± 1 , ± 2 , ± 3 , ± 4 , ± 6 , ± 8 , ± 1 2 , ± 2 4 ) . Checking it manually, it's possible to see that 2 , 3 and 4 are roots.
So, the smallest root is 2 and the condition of the semi-perimeter gives:
2 4 6 6 − x = 2
x = 2 3 1
The equation of the perimeter is, then:
x + y + z = 4 6 6
y + z = 2 3 5
The condition of the ratio between the area and the square root of the perimeter, using the triangle's area general formula gives:
( x + y + z ) 4 1 ( x + y + z ) ⋅ ( x + y − z ) ⋅ ( x − y + z ) ⋅ ( − x + y + z ) = 1 2 8 3 4
The perimeter inside the numerator will cancel out with the denominator:
( x + y − z ) ⋅ ( x − y + z ) ⋅ ( − x + y + z ) = 4 1 2 8 3 4
The terms inside the square root can be rewritten as:
( x + y + z − 2 z ) ⋅ ( x + y + z − 2 y ) ⋅ ( x + y + z − 2 x ) = 4 1 2 8 3 4
( 4 6 6 − 2 z ) ⋅ ( 4 6 6 − 2 y ) ⋅ ( 4 ) = 4 1 2 8 3 4
( 4 6 6 − 2 z ) ⋅ ( 4 6 6 − 2 y ) ⋅ 4 = 1 6 ⋅ 1 2 8 3 4
2 1 7 1 5 6 − 4 6 6 ⋅ 2 ⋅ ( y + z ) + 4 y z = 5 1 3 3 6
Since y + z = 2 3 5 :
y z = 1 3 3 0 0
Solving:
y z = 1 3 3 0 0
y + z = 2 3 5
One gets:
y = 1 4 0 , z = 9 5
Or:
y = 9 5 , z = 1 4 0
Solving for the first condition ( y = 1 4 0 , z = 9 5 ):
− a b c = 2 3 1
1 0 ( a + b + c ) = 1 4 0
2 0 ( a b + a c + b c ) = 9 5
One gets six possible solutions:
a = − 3 . 5 , b = 5 . 5 , c = 1 2
a = − 3 . 5 , b = 1 2 , c = 5 . 5
a = 5 . 5 , b = − 3 . 5 , c = 1 2
a = 5 . 5 , b = 1 2 , c = − 3 . 5
a = 1 2 , b = − 3 . 5 , c = 5 . 5
a = 1 2 , b = 5 . 5 , c = − 3 . 5
Solving for the second condition ( y = 9 5 , z = 1 4 0 ), a , b and c will have non-real solutions.
So, the only possible solutions for a , b and c are the ones with:
x = 2 3 1 , y = 1 4 0 , z = 9 5
Also, ( a , b , c ) will be permutations of the set ( 1 2 , 5 . 5 , − 3 . 5 )
And the digit sum of a , b and c in any of the six cases, i.e., in any of the permutations is:
3 + 5 + 5 + 5 + 1 + 2 = 2 1