<PRE><B>Question 1028960</B>
using calculus and taking the derivative
x^3-9x^2+23x-15=0
Test each.
1 works, and it does for all choices
for 5, 125-225+115-15=0, so 5 works.  
for 3, 27-81+69-15=0
It is C.
{{{graph(300,200,-10,10,-10,10,(1/4)x^4-3x^3+(23/2)x^2-15x)}}}

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