Let a > b > c be the roots of the equation ( x − 1 ) 3 + ( x + 3 ) 3 = 4 2 ( x + 1 )
The value of
( a + b 1 + a + c 1 + b + c 1 ) ( a − b + c ) ( a a + b b a + b ) ( a + b c + c )
can be written as n m , where m and n are positive coprime numbers. Evaluate 3 m m − n 2 + 2 0 m m + n m − m .
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First we want to find the roots of the equation, a, b, c.
To do this we will expand the equation and then factorise.
The equation expands to 2 x 3 + 6 x 2 − 1 2 x − 1 6
Factorising this we get the equation 2 ( x − 2 ) ( x + 1 ) ( x + 4 )
The roots of this equation are x = 2 , x = − 1 , x = − 4
Therefore a = 2 , b = − 1 , c = − 4
Substituting into the equation
( a + b 1 + a + c 1 + b + c 1 ) ( a − b + c ) ( a a + b b a + b ) ( a + b c + c )
( 2 − 1 1 + 2 − 4 1 + − 1 − 4 1 ) ( 2 + 1 − 4 ) ( 2 2 + − 1 − 1 2 − 1 ) ( 2 + − 1 ( − 4 ) + c )
Which then simplifies to 3 1 0 1
3 1 0 = n m
Substituting into the equation
3 m m − n 2 + 2 0 m m + n m − m .
3 ( 1 0 1 0 ) − 3 2 + 2 0 1 0 1 0 + 3 1 0 − 1 0 .
Which simplifies to 1 0 2 4
2 1 0
2 5
= 3 2