Math Problems : Quadratic Equation

Question

For what value of m will the roots of the quadratic equation x² + mx + 4 = 0 have real and equal roots?

4
-4
4 or -4
16

Correct Answer

Choice (3). 4 or -4

Explanatory Answers

The question states that the roots of the equation are real and equal.

Note

The roots of a quadratic equation of the form ax² + bx + c = 0 will be real and equal if its discriminant D = b² - 4ac = 0

In this case, b = m, a = 4 and c = 4.
Therefore, m² - 4 * 4 * 1 = 0

Or m² = 16

Orr m = +4 or m = -4.

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