Question:

The sum of roots of |x2 - 8x + 15| - 2x + 7 = 0 is:

Updated On: Nov 7, 2024
  • \(11+\sqrt{3}\)
  • \(11-\sqrt{3}\)
  • \(9+\sqrt{3}\)
  • \(9-\sqrt{3}\)
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The Correct Option is C

Solution and Explanation

\(|x^{2}-8x+15|=2x-7\)

Case-I \(x\geq 5\)

\(x^{2}-10x+22=0\)

\(x=\frac{10\pm \sqrt{12}}{2}=5\pm \sqrt{3}\)

then \(x= 5+\sqrt{3}\)

Case-II : \(\frac{7}{2}\leq x\leq 5\)

\(x^{2}-8x+15=7-2x\)

\(x^{2}-6x+8=0\)

\(x=4\)

Therefore, the sum of the roots \(= 5+\sqrt{3}+4=9+\sqrt{3}\)
So, The correct option is (C): 9 + \(\sqrt{3}\)

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Concepts Used:

Quadratic Equations

A polynomial that has two roots or is of degree 2 is called a quadratic equation. The general form of a quadratic equation is y=ax²+bx+c. Here a≠0, b, and c are the real numbers

Consider the following equation ax²+bx+c=0, where a≠0 and a, b, and c are real coefficients.

The solution of a quadratic equation can be found using the formula, x=((-b±√(b²-4ac))/2a)

Two important points to keep in mind are:

  • A polynomial equation has at least one root.
  • A polynomial equation of degree ‘n’ has ‘n’ roots.

Read More: Nature of Roots of Quadratic Equation

There are basically four methods of solving quadratic equations. They are:

  1. Factoring
  2. Completing the square
  3. Using Quadratic Formula
  4. Taking the square root