SOLUTION: what is the inverse of f(n)= -1-2n^3

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Question 996944: what is the inverse of f(n)= -1-2n^3
Found 2 solutions by MathLover1, stanbon:
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!

to find the inverse of f%28n%29=+-1-2n%5E3, first recall that f%28n%29=+y
so, we have y=+-1-2n%5E3-> now swap n and y

n=+-1-2y%5E3...solve for y

2y%5E3=+-1-n

y%5E3=+-%281%2Bn%29%2F2

y=+root%283%2C-%281%2Bn%29%2F2%29->your inverse

f%5E-1%28n%29=+root%283%2C-%281%2Bn%29%2F2%29
or
f%5E-1%28n%29=+root%283%2C-%281%2Bn%29%29%2Froot%283%2C2%29

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
what is the inverse of f(n)= -1-2n^3
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1st:: Interchange x and y to get:
x = -1 - 2y^2
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2nd: Solve for "y"::
2y^2 = -1-x
----
y^2 = -(x+1)/2
----
y = +/-sqrt[-(x+1)/2]
------------------------
That is the inverse.
Cheers,
Stan H.