Verified Answer :

  • Identify coefficients of the quadratic expression \(x^2 - 11x + 28\), where \(b = -11\) and \(c = 28\).
  • Determine two negative factors of \(28\) that sum to \(-11\), which are \(-4\) and \(-7\).
  • Write the expression in factored form as \((x - 4)(x - 7)\).
  • The final result is \(\boxed{(x - 4)(x - 7)}\).

Explanation

  1. Problem Analysis

We are given the quadratic expression \(x^2 - 11x + 28\). This is a quadratic trinomial of the form \(ax^2 + bx + c\), where the leading coefficient \(a = 1\), the coefficient \(b = -11\), and the constant term \(c = 28\). Our goal is to factor this expression into the product of two linear binomials of the form \((x + p)(x + q)\), where \(p\) and \(q\) are constants. Expanding this product, we get \(x^2 + (p + q)x + pq\). Thus, we need to find two numbers \(p\) and \(q\) such that their sum \(p + q = -11\) and their product \(pq = 28\).

  1. Finding the Factors

To find the values of \(p\) and \(q\), we look for factors of the constant term \(c = 28\). Since the product \(pq = 28\) is positive and the sum \(p + q = -11\) is negative, both \(p\) and \(q\) must be negative numbers. Let us list the pairs of negative factors of \(28\):

  • \(-1\) and \(-28\): sum is \(-1 + (-28) = -29\)
  • \(-2\) and \(-14\): sum is \(-2 + (-14) = -16\)
  • \(-4\) and \(-7\): sum is \(-4 + (-7) = -11\)

The pair that satisfies the condition that their sum is \(-11\) is \(-4\) and \(-7\).

  1. Final Factoring and Verification

Now that we have identified the constants \(p = -4\) and \(q = -7\), we can substitute them into the factored form \((x + p)(x + q)\). This gives us the expression \((x - 4)(x - 7)\). We can verify this by expanding the product: \((x - 4)(x - 7) = x \cdot x + x \cdot (-7) + (-4) \cdot x + (-4) \cdot (-7) = x^2 - 7x - 4x + 28 = x^2 - 11x + 28\). Since this matches our original expression, the factoring is correct. The final factored form is \(\boxed{(x - 4)(x - 7)}\).

Examples

Factoring quadratic expressions is a fundamental skill in algebra used to solve problems across many disciplines. For example, if you are designing the layout of a rectangular garden and you know its area is represented by the quadratic equation \(x^2 - 11x + 28 = 0\), factoring helps you find the dimensions of the garden. By setting the factors \((x - 4) = 0\) and \((x - 7) = 0\), you can quickly determine that the side lengths must be \(4\) units and \(7\) units. This simplifies complex problems involving areas, projectile motion, and optimization into manageable linear equations.