Question:

Let a, b, c be real numbers such that $a + b + c < 0$ and the quadratic equation $ax^2 + bx + c = 0$ has imaginary roots. Then

Updated On: Apr 30, 2024
  • $a > 0, c > 0$
  • $a > 0, c < 0$
  • $a < 0, c > 0$
  • $a < 0, c < 0$
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The Correct Option is D

Solution and Explanation

$f\left(x\right) = ax^{2}+bx+c, \,f\left(1\right) < 0\,so\,f\left(x\right) < 0 \,\forall\, x \in R \Rightarrow f\left(0\right) < 0 \Rightarrow c < 0 \Rightarrow a < 0\,and\,c < 0$
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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