how do i factor this?

Question

x^3-21x+20

Answer 1

f(x) = x³ - 21x + 20
f(1) = 1 - 21 + 20 = 0
Thus (x - 1) is a factor
To find other factors , use synthetic division to divide by x - 1 :-
1 | 1***0***-21***20
********1*****1***-20
--------------------------
***1***1****- 20****0
Other factor is x² + x - 20 = (x + 5) (x - 4)
f(x) = (x - 1) (x + 5) (x - 4)

Answer 2

The rule is if the second to last term is greater (take absolute value) than the last term, begin long division with x-1, if it is smaller, divide with x+1.
|-21|>20 so divide by x-1
x-1 into x^3-21x+20
do long division, you get
(x^2+x-20)(x-1)
then simplify (x^2+x-20)
(x+5)(x-4)(x-1)

Answer 3

♠ x^3 –21x +20=0; use theorem of rational roots;
(x-1) (x-4) (x+5) =0;

Answer 4

is it x^2-21x+20 instead, please recheck ur question

ill assume it to be x^2 - 21x + 20

x^2- 20x- x + 20 = 0

x(x-20)-1(x-20)=0

(x-20) (x-1)=0

x=20 or x=1

if it is x^3-21x=20, use the quadratic formula.

Answer 5

=(x-1)(x-20)

Answer 6

this is an algbra equation. x times then takeaway 21 then times by X and add 20.