How many and of which kind of roots does the equation f(x) = x3 – x2 – x + 1 have?
A. 2 real; 1 complex
B. 1 real; 2 complex
C. 3 real
D. 3 complex

Respuesta :

C i think.................

The kind of roots does the equation f(x) is option (C) 3 real roots is the correct answer.

What is a polynomial equation?

A polynomial equation is a sum of constants and variables. A polynomial is an expression consisting of indeterminate's (also called variables) and coefficients, that involves only the operations of addition, subtraction, multiplication, and non-negative integer exponentiation of variables.

For the given situation,

The equation [tex]f(x) = x^3 - x^2 - x + 1[/tex]

The roots of the polynomial equation can be found as follows,

Step 1:

Substitute the value of x in which the equation f(x) equals zero.

⇒ Put [tex]x = 1[/tex], the equation becomes

⇒ [tex]f(1) = 1^3 - 1^2 - 1 + 1[/tex]

⇒ [tex]f(1) = 0[/tex]

Thus [tex](x - 1)[/tex] is the one root of the equation.

Step 2:

The other roots can be found by framing the quadratic equation on dividing the equation [tex]f(x) = x^3 - x^2 - x + 1[/tex] by [tex](x - 1)[/tex]

On dividing [tex]f(x) = x^3 - x^2 - x + 1[/tex] by [tex](x - 1)[/tex] we get the quotient,

⇒ [tex](x^{2} -1)[/tex]

Step 3:

Now factorize the quadratic equation, [tex](x^{2} -1)[/tex]

It can be expand using the identity,

⇒ [tex](x^{2} -1^{2} ) = (x+1)(x-1)[/tex]            [∵ (a^2 - b^2) = (a+b)(a-b) ]

Thus the factors of the equation are [tex](x-1)(x+1)(x-1)[/tex]. So the roots are [tex]1,-1,1[/tex].

Hence we can conclude that the kind of roots does the equation f(x) is option (C) 3 real roots is the correct answer.

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