If (x-1) is a factor of the polynomial f(x)=4x³−4x²−x−k Factorize completely and state it's zeros. Do this without leaving out any details

Mathematics

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Answer

f(x)=(x−1)(2x−1)(2x+1)f(x) = (x-1)(2x-1)(2x+1)

1,12,−121, \frac{1}{2}, -\frac{1}{2}

Step-by-step solution

6 steps
  1. Find the value of kk using the Factor Theorem.

    If (x−1)(x-1) is a factor of f(x)f(x), then f(1)=0f(1) = 0.
    Substitute x=1x=1 into the polynomial f(x)=4x3−4x2−x−kf(x) = 4x^3 - 4x^2 - x - k:

    f(1)=4(1)3−4(1)2−(1)−kf(1) = 4(1)^3 - 4(1)^2 - (1) - k 0=4(1)−4(1)−1−k0 = 4(1) - 4(1) - 1 - k 0=4−4−1−k0 = 4 - 4 - 1 - k 0=−1−k0 = -1 - k k=−1k = -1
  2. Substitute the value of kk back into the polynomial.

    The polynomial becomes:

    f(x)=4x3−4x2−x−(−1)f(x) = 4x^3 - 4x^2 - x - (-1) f(x)=4x3−4x2−x+1f(x) = 4x^3 - 4x^2 - x + 1
  3. Factorize the polynomial using synthetic division.

    Since (x−1)(x-1) is a factor, we divide f(x)f(x) by (x−1)(x-1).
    Using synthetic division with the root x=1x=1:

    1 | 4  -4  -1   1
      |    4   0  -1
      ----------------
        4   0  -1   0
    

    The quotient is 4x2+0x−14x^2 + 0x - 1, which simplifies to 4x2−14x^2 - 1.
    So, f(x)=(x−1)(4x2−1)f(x) = (x-1)(4x^2 - 1).

  4. Factorize the quadratic expression completely.

    The quadratic expression 4x2−14x^2 - 1 is a difference of squares, a2−b2=(a−b)(a+b)a^2 - b^2 = (a-b)(a+b), where a=2xa=2x and b=1b=1.

    4x2−1=(2x)2−(1)2=(2x−1)(2x+1)4x^2 - 1 = (2x)^2 - (1)^2 = (2x - 1)(2x + 1)
  5. Write the completely factorized polynomial.

    Substitute the factored quadratic back into the expression for f(x)f(x):

    f(x)=(x−1)(2x−1)(2x+1)f(x) = (x-1)(2x-1)(2x+1)

    The completely factorized polynomial is f(x)=(x−1)(2x−1)(2x+1)\boxed{f(x) = (x-1)(2x-1)(2x+1)}.

  6. State the zeros of the polynomial.

    To find the zeros, set each factor equal to zero and solve for xx:
    For the first factor:

    x−1=0  ⟹  x=1x-1 = 0 \implies x = 1

    For the second factor:

    2x−1=0  ⟹  2x=1  ⟹  x=122x-1 = 0 \implies 2x = 1 \implies x = \frac{1}{2}

    For the third factor:

    2x+1=0  ⟹  2x=−1  ⟹  x=−122x+1 = 0 \implies 2x = -1 \implies x = -\frac{1}{2}

    The zeros of the polynomial are 1,12,−12\boxed{1, \frac{1}{2}, -\frac{1}{2}}.

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