If are the distinct roots of , such that .
Find .
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Given polynomial : x 3 − 2 7 x 2 − 3 0 8 1 x − 3 0 5 3 = 0
By possible rational root theorem , we can easily figure out that − 1 is a root of this polynomial.
Thus, By Factor theorem , ( x + 1 ) is a factor of x 3 − 2 7 x 2 − 3 0 8 1 x − 3 0 5 3 = 0 .
Thus by Division algorithm the given polynomial can be written as :
x 3 − 2 7 x 2 − 3 0 8 1 x − 3 0 5 3 = ( x + 1 ) ( x 2 − 2 8 x − 3 0 5 3 ) = 0
Since we have already got − 1 as a root ,
( x 2 − 2 8 x − 3 0 5 3 ) = 0
( x − 7 1 ) ( x + 4 3 ) = 0 This gives us that 7 1 , − 4 3 are the other roots of the polynomial.
Thus , a = 7 1 , b = − 1 , c = − 4 3 ⇒ 2 a + 7 b + c = 2 ( 7 1 ) + 7 ( − 1 ) + ( − 4 3 ) = 9 2