To solve the infinite nested cube root expression (\sqrt[3]{x + 3\sqrt[3]{x + 3\sqrt[3]{x + \dotsb}}}), follow these steps:
Step 1: Define the expression as (y)
Let (y = \sqrt[3]{x + 3\sqrt[3]{x + 3\sqrt[3]{x + \dotsb}}}).
Since the expression is infinite, the inner nested part is identical to (y). Thus:
(y = \sqrt[3]{x + 3y})
Step 2: Cube both sides
Eliminate the cube root by cubing both sides:
(y^3 = x + 3y)
Rearranged: (y^3 - 3y - x = 0)
Step 3: Assume a common value for (x)
A typical problem uses (x=2) (a standard case). Substitute (x=2):
(y^3 - 3y - 2 = 0)
Factor the equation:
((y+1)^2(y-2) = 0)
The real root is (y=2) (since ((y+1)^2 \geq 0)).
Answer: (\boxed{2})


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