## DeadShot 3 years ago Determine the zeros of f(x) = x3 - 12x2 + 28x - 9.

1. anonymous

try factoring :)

so, I'd remove the x^2 from the first two terms, making it x^2 (x - 12 + 28x - 9)?

and then combine like terms, making it x^2 (29x - 21)

4. anonymous

... you can't just remove x^2 from the front. what about the back? you get x^2(x - 12) + 28x - 9

5. anonymous

start by hit and tril, put x=1, -1, 2, -2 till u get f(x)=0

ok

7. anonymous

|dw:1359226096145:dw|

8. anonymous

|dw:1359226195996:dw|

9. anonymous

try ur self till u get f(x)=0 after that v proceed next

ok

11. anonymous

let "a" is that value i-e f(a)=0 means "a" is a root and x-a is a factor, now divide the original equation by x-a to get another factor(that will b quadratic, factorize that and equate the three factors one by one to get the roots,

12. anonymous

my laptop battery is low , m about to offline if i didnt reach power on time, good luck for the question

I couldn't find any numbers that made f(x)=0

14. anonymous

ok sigh i don't know what he was doing

15. anonymous

but via factoring you get (x-9)(x^2-3x+1)

16. anonymous

therefore x = 9 and you use the quadratic formula to find the roots for x^2 - 3x + 1

I'm having trouble using the quadratic formula with (x^2 - 3x + 1)

18. anonymous

$a=1,b=-3,c=1$ $x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$