Question 1128664
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The statement of the problem asks you to find the value of x for which the value of the given function is -7.  So<br>
{{{x^3+5x-1 = -7}}}
{{{x^3+5x+6 = 0}}}<br>
Synthetic substitution (or any of a number of other methods) finds a real solution is x = -1; it turns out the other two solutions are complex.  So<br>
ANSWER: f^(-1)(-7) = -1