## burhan101 Group Title x intercept for this function one year ago one year ago

1. burhan101 Group Title

$\huge y=x^3-9x^2+15x+4$

2. burhan101 Group Title

this is unfactorable?

3. timo86m Group Title

oh no wait nevermind

4. SmoothMath Group Title

Any particular method they want you to use? Do they specify factoring?

5. burhan101 Group Title

No but isnt that the only way?

6. SmoothMath Group Title

Graphing is the easiest.

7. SmoothMath Group Title

Graph that bad boy. Look for where it crosses the x axis. Doneso.

8. burhan101 Group Title

no i have to use an algebraic method

9. burhan101 Group Title

because like say on an exam, i cant graph that

10. Mertsj Group Title

Possible rational roots are :

11. SmoothMath Group Title

Okay then your best best is to use the rational root theorem to list possible rational roots. Then check each one to see if it is a valid root.

12. Mertsj Group Title

$\pm1,\pm4,\pm2$

13. Mertsj Group Title

Use synthetic division to see if any of those are actual roots.

14. SmoothMath Group Title

Mertsj is correct. The way he got those possible roots is: A: Make a list of factors for the last number (In this case, it's 4) B: Make a list of factors for the first coefficient (In this case, it's 1) Possible rational roots must be of the form $$\huge \frac{\text{things in the first list}}{\text{things in the second list}}$$

15. Mertsj Group Title

It is not factorable.

16. Mertsj Group Title

So the best approach would be to find where y changes sign. Then you would know there is a root between those two values and you could hone in on it by trial and error. Of if you know calculus, you could use the derivative. What class is this for?

17. burhan101 Group Title

@Mertsj calculus !

18. oldrin.bataku Group Title

they want you to bruteforce using newton's more than likely