f(x) =
x^3-3x^2x+4x-2
Rational zero test is a way of finding the
zeros of a polynomial by looking at the factors of the constant term divided by the
coefficient of the laeding term of the polymials.; and we can try around + or - factors
also.
In this case , constant term = -2 and leading term is
x^3 and coefficient of x^3 is 1. So, constant term / coeff of x^3 = -2. The factors of
-2 are : -2 , -1 ,2 and 2. Try which of them make f(x) = 0, by
substitution.
The sum of the coefficients of powers of x is
zero. So f(1) = 1^3-3*1^2+4*1-2 = 0. Thus by rational zero test 1 is zero the polynomial
f(x).
Therefore x-1 is a factor by remainder therem. So we
divide f(x) by (x-1).
x-1)x^3-3x^2+4x-2 (
x^2
x^3-x^2
-----------------
x-1)-2x^2
+4x ( x^2 -2x
-2x^2
+2x
-------------------------------
x-1) 2x-2
(
x^2-2x(x^2-2x+2
2x-2
---------------------------------------
0
So f(x) /x-1 =
x^2-2x+2.
Therefore f(x) = x^3-3x^2+4x-2 = (
x-1)(x^2-2x+2).
Bur x^2-2x+2 has no real factors ( no
real zeros of the polynomial f(x) ), as the discriminant of x^2-2x+2 is (-2)^2 - 4*1*2
= 4-8 = -4 < 0.
So the only linear factor of
x^3-3x^2+4x+2 is (x-1).
Hope this
helps.
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