Question 237141
x^4-5x^2-36
(x^2-9)(x^2+4)
(x+3)(x-3)(x^2+4)
{{{ graph( 300, 200, -6, 5, -50, 10, x^4 -5x^2 -36) }}} (graph 300x200 pixels, x from -6 to 5, y from -50 to 10, x^4 -5x^2 -36). 
Use +3 & -3 for your synthetic divison.