Saturday, May 22, 2010

Double roots help?

Find C such that polynomial function f(x)=4x^3 + Cx - 27 has a double root

Double roots help?
If f(x) has a double root this also root of the derivative


f´(x) =12x^2+C=0 so x=+-sqrt(-C/12) so C must be negative


so C=-27 and x= -sqrt(27/12) =-3/2


No comments:

Post a Comment