Use the rational root theorem to list all possible rational roots for the equation x3 - x2 - x - 3 = 0
-3, -1, 1, 3
1, 3
-3, 3
No roots
Solution:
Using the rational root theorem, which states that, if the polynomial f(x) = anxn + an - 1xn - 1 +...+ a1x + a0 has integer coefficients, then every rational zero of f(x) has the form p/q where p is a factor of the constant term a0 and q is a factor of the leading coefficient an.
The given equation is
x3 - x2 - x - 3 = 0
We know that ±1 are ±3 factors of 3
f(x) = x3 - x2 - x - 3 = 0
f(1) = 13 - 12 - 1 - 3
f(1) = 1 - 1 - 1 - 3
f(1) = 1 - 5
f(1) = -4
f(-1) = (-1)3 - (-1)2 - (-1) - 3
f(-1) = -1 - 1 + 1 - 3
f(-1) = -1 - 3
f(-1) = -4
f(3) = 33 - 32 - 3 - 3
f(3) = 27 - 9 - 3 - 3
f(3) = 27 - 15
f(3) = 12
f(-3) = (-3)3 - (-3)2 - (-3)- 3
f(-3) = -27 - 9 + 3 - 3
f(-3) = -39 + 3
f(-3) = -36
Therefore, there are no roots.
Use the rational root theorem to list all possible rational roots for the equation x3 - x2 - x - 3 = 0
Summary:
Using the rational root theorem, there are no roots for the equation x3 - x2 - x - 3 = 0 are 1, -1, 3 and -3.
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