Find the minimum root of that satisfy the equation above.
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I know this way is a bit too tedious, but I'm posting this anyway.
For all x = ± 1 , multiplying both sides by 2 ( x 2 − 1 ) we get:
3 ( x − 2 ) + 4 2 x 3 − 3 x + 1 = 2 ( x 2 − 1 )
⇔ 4 2 x 3 − 3 x + 1 = 2 x 2 − 3 x + 4
As 2 x 2 − 3 x + 4 > 0 for all real x , we can square both sides:
1 6 ( 2 x 3 − 3 x + 1 ) = ( 2 x 2 − 3 x + 4 ) 2
⇔ 1 6 ( 2 x 3 − 3 x + 1 ) = 4 x 4 − 1 2 x 3 + 2 5 x 2 − 2 4 x + 1 6
⇔ 4 x 4 − 4 4 x 3 + 2 5 x 2 + 2 4 x = 0
⇔ x ( 2 x + 1 ) ( 2 x 2 − 2 3 x + 2 4 ) = 0
Two roots of 2 x 2 − 2 3 x + 2 4 are both positive because their sum is 2 2 3 > 0 and their product is 1 2 > 0 Hence the minimum root is x = − 2 1