Question

Difficulty: MediumMultiplying Polynomials

Which of the following represents the fully simplified form of the expression (3x−4)2−x(2x+5)(3x - 4)^2 - x(2x + 5)?

  1. A
    7x2−19x+167x^2 - 19x + 16
  2. B
    7x2−5x+167x^2 - 5x + 16
  3. C
    7x2−29x−167x^2 - 29x - 16
  4. 7x2−29x+167x^2 - 29x + 16Answer

Answer

The correct simplified expression is 7x2−29x+167x^2 - 29x + 16.
Expanding the squared binomial yields 9x2−24x+169x^2 - 24x + 16. Distributing the −x-x yields −2x2−5x-2x^2 - 5x. Combining the like terms gives (9x2−2x2)+(−24x−5x)+16(9x^2 - 2x^2) + (-24x - 5x) + 16, which simplifies perfectly to 7x2−29x+167x^2 - 29x + 16.

Step-by-Step Solution

1
Expand the squared binomial (3x−4)2(3x - 4)^2.
(3x)2−2(3x)(4)+42=9x2−24x+16(3x)^2 - 2(3x)(4) + 4^2 = 9x^2 - 24x + 16
Using the perfect square formula (a−b)2=a2−2ab+b2(a - b)^2 = a^2 - 2ab + b^2 is required to properly multiply the binomial by itself.
2
Distribute the term −x-x across the binomial (2x+5)(2x + 5).
−x(2x)−x(5)=−2x2−5x-x(2x) - x(5) = -2x^2 - 5x
The distributive property must be applied, ensuring the negative sign is carried to both terms inside the parentheses.
3
Combine the results from the previous steps and combine like terms.
(9x2−24x+16)+(−2x2−5x)=(9x2−2x2)+(−24x−5x)+16=7x2−29x+16(9x^2 - 24x + 16) + (-2x^2 - 5x) = (9x^2 - 2x^2) + (-24x - 5x) + 16 = 7x^2 - 29x + 16
Like terms (those with the same variable raised to the same power) must be grouped and added together to find the fully simplified polynomial form.

Key Concept

Expanding perfect square binomials and distributing monomial terms correctly.
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