Find all of the real and imaginary zeros for the polynomial function. f(x)=X^3-4x^2-36x+144

Question

anonymous · Answer

I know one of the zeros is positive 4.  The other one I had down was plus or minus 6i (This was circled and I was given half credit).  What's wrong with this?

anonymous · Answer

@campbell_st

anonymous · Answer

$$x^3-4 x^2-36x+144=(x-6) (x-4) (x+6)  $$

campbell_st · Answer

Ok... so if 4 is a zero then (x - 4) is a factor so a little division again

|dw:1381733426955:dw|

so the factors are 

$$(x-4)(x^2 - 36)$$

factor the quadratic, which is the difference of 2 squares... 

for the 3 linear factors