Refer to the following equation:
This equation has only one real solution x. Can you find ?
(Write your answer by two decimal places.)
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y = x 5 + x 4 + 1
y = x 5 + x 4 + x 3 − x 3 + 1
y = x 3 ( x 2 + x + 1 ) − ( x − 1 ) ( x 2 + x + 1 )
y = ( x 2 + x + 1 ) ( x 3 − x + 1 )
Now, as ( x 2 + x + 1 ) has imaginary roots, x 3 − x + 1 is the one with 1 real root
x 3 − x + 1 = 0
Now, graph of x 3 − x is
So, graph of x 3 − x + 1 will be above graph shifted one unit up. It will intersect x-axis at about -1.32. So,
∣ R o o t ∣ = 1 . 3 2
Note: I drew graph myself while solving. Above graph from Wolfram Alpha is taken for explaining.