If the value of for which the above equation has exactly one root independent of is in the form where and are coprime positive integers , find .
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Let the expression be f(x). Write it as g ( x ) + λ p ( x ) and since roots are independent of λ we must have g ( x ) = p ( x ) = 0 (at same value of x ) so that f ( x ) = 0 irrespective of λ .
f ( x ) = ( g ( x ) x 5 − x 3 − 4 x 2 − 3 x − 2 ) + λ ( p ( x ) 5 x 4 + α x 2 − 8 x + α ) = 0
g ( x ) = 0 ⟹ ( x − 2 ) ( x 4 + 2 x 3 + 3 x 2 + 2 x + 1 ) = 0 ⟹ ( x − 2 ) ( x 2 + x + 1 ) 2 = 0
Since f ( x ) has only one solution i.e x = 2 . Now since x = 2 setting p ( 2 ) = 0 we get α = 5 − 6 4 . Hence 6 4 + 5 = 6 9 .
Hence f ( x ) has only one root and independent of λ f ( x ) vanishes at x = 2 when α = 5 − 6 4 .