Which expression is a difference of squares with a factor of $5x - 8$?


A$25x^2 - 16$
B$25x^2 + 16$
C$25x^2 - 64$
D$25x^2 + 64$

Verified Answer :

  • The difference of squares formula is \(A^2 - B^2 = (A - B)(A + B)\).
  • Testing the required factor \(5x - 8\) suggests an expression of the form \((5x)^2 - 8^2\), which is \(25x^2 - 64\).
  • Factoring \(25x^2 - 64\) gives \((5x - 8)(5x + 8)\), confirming it has the required factor.
  • Final Answer: \(\boxed{25x^2 - 64}\)

Explanation

  1. Analyzing the Problem using the Difference of Squares Identity

To determine which expression is a difference of squares and has a factor of \(5x - 8\), we first recall the identity for the difference of squares: \[A^2 - B^2 = (A - B)(A + B).\] We are looking for an expression of the form \(A^2 - B^2\) where one of the factors is \(5x - 8\). This means that \(A = 5x\) and \(B = 8\), so our expression must take the form \((5x)^2 - 8^2 = 25x^2 - 64.\)

  1. Evaluating the Given Options

Now we evaluate each of the given options:

  1. \(25x^2 - 16\): This is a difference of squares, specifically \((5x)^2 - 4^2\), which factors as \((5x - 4)(5x + 4)\). This does not contain the factor \(5x - 8\).
  2. \(25x^2 + 16\): This is a sum of squares, not a difference of squares.
  3. \(25x^2 - 64\): This is a difference of squares, specifically \((5x)^2 - 8^2\). Using the formula, it factors as \((5x - 8)(5x + 8)\). This clearly contains the factor \(5x - 8\).
  4. \(25x^2 + 64\): This is a sum of squares, not a difference of squares.
  1. Conclusion

By comparing our derived target expression \(25x^2 - 64\) with the provided choices, we confirm that the correct expression is indeed \(25x^2 - 64\). Therefore, the difference of squares that includes \(5x - 8\) as a factor is \(\boxed{25x^2 - 64}\).

Examples

In architecture or construction, you might need to determine the area of a specific section of a floor plan. If you have a square room of side length \(5x\) and you remove a square cutout of side length \(8\) from the corner, the remaining area can be expressed as \((5x)^2 - 8^2\). Understanding how to factor this as \((5x - 8)(5x + 8)\) helps in simplifying design calculations and material estimations, making it easier to plan for flooring or tile layouts that need to fit around such features.