Question 1074062
Best to use lower-case i instead of I, for the imaginary unit.


The other root is  {{{5-i}}}.


{{{(x-(5+i))(x-(5-i))(x+4)}}}
Do the steps...
{{{(x^2-10x+26)(x+4)}}}
{{{highlight(x^3-6x^2-14x+52)}}}