Solving for x Intercepts to Polynomial Functions

[dcgirl16]

I'm having trouble finding x intercepts i have the question x^3-9x^2+15x+30 and by setting y=0 i got -30=x(x^2-9x+15) I used the quadratic formula to find that x^2-9x+15 give me no real roots, so the only intercept would be x=0. But this would also mean that the yintercept is 0 and i found that it is 30. What am i doing wrong is it something to do with moving the 30 to the left side?

 

[malawi_glenn]

-30=x(x^2-9x+15)

You can not solve the right hand side to be = 0 if you have left hand side = -30 ...

 

[dcgirl16]

so how do i do it. i was moving that over to solve for x

 

[malawi_glenn]

test solution, then rewrite x^3-9x^2+15x+30 as (x+n)(x-b)(x-4) or something in that style.

If c solves the p(x) = then p(x) can be divided with (x-c)..
and vice versa, (x+r) ; P(-r) = 0