What is the approximate real non-integral solution of the equation above? Round your answer to two decimal places.
Details and Assumptions
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We note that x 2 − 4 x + 5 = 2 x − 2 ⇒ ( x − 2 ) 2 + 1 = 2 x − 2
Let y = x − 2 ⇒ f ( y ) = y 2 + 1 − 2 y = 0
⇒ f ′ ( y ) d y d f ( y ) = 2 y − ln 2 ˙ 2 y
We note that: f ( 4 ) = 1 and f ( 5 ) = − 6 implying there is a root within 4 < y < 5 . Using Newton's method, we have:
y n + 1 = y n − f n ′ ( y ) f n ( y )
y n 4 4 . 3 2 3 5 8 7 4 3 1 4 . 2 6 0 5 8 5 5 7 3 4 . 2 5 7 4 6 9 2 8 9 4 . 2 5 7 4 6 1 9 1 4 f ( y n ) 1 − 0 . 3 2 9 6 0 8 2 4 4 − 0 . 0 1 4 8 4 8 1 0 9 − 3 . 4 9 7 2 2 × 1 0 − 0 5 − 1 . 9 5 4 8 8 × 1 0 − 1 0 f ′ ( y n ) − 3 . 0 9 0 3 5 4 8 8 9 − 5 . 2 3 1 7 2 2 5 8 4 − 4 . 7 6 4 6 8 4 1 3 9 − 4 . 7 4 2 2 4 9 6 5 5 − 4 . 7 4 2 1 9 6 6 3 8 f ′ ( y n f ( y n ) − 0 . 3 2 3 5 8 7 4 3 1 0 . 0 6 3 0 0 1 8 5 8 0 . 0 0 3 1 1 6 2 8 4 7 . 3 7 4 6 × 1 0 − 0 6 4 . 1 2 2 3 1 × 1 0 − 1 1
Therefore, y ≈ 4 . 2 5 7 4 6 1 9 1 4 ⇒ x = y + 2 ≈ 6 . 2 6 .