Find the sum of all real values of satisfying the equation above.
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x x x x 3 x 3 x 3 − x 2 − x + 2 ⟹ u 2 − 2 u + 1 ( u − 1 ) 2 u x 3 − x 2 − x + 1 x 3 − x 2 − x + 1 x ( x 2 − x − 1 ) = x − x 1 + 1 − x 1 = x 2 − 1 + x − 1 = x − 1 ( x + 1 + 1 ) = ( x − 1 ) ( x + 1 + 2 x + 1 + 1 ) = x 2 + x − 2 + 2 ( x + 1 ) ( x 2 − 2 x + 1 ) = 2 x 3 − x 2 − x + 1 = 0 = 0 = 1 = 1 = 1 = 0 Multiply both sides by x Squaring both sides Let u = x 3 − x 2 − x + 1
⟹ ⎩ ⎪ ⎪ ⎪ ⎪ ⎨ ⎪ ⎪ ⎪ ⎪ ⎧ x = 0 x = 2 1 + 5 x = 2 1 − 5
But only x = 2 1 + 5 = φ , the golden ratio, satisfies the original equation. Therefore the sum of all real value of x satisfying the equation is φ ≈ 1 . 6 1 8 .