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Question

If the roots of the quadratic equation $kx^2 – 4x + 1 = 0$ are real and equal, what is the value of k?

The correct answer is
4

This problem involves finding the value of a coefficient in a quadratic equation based on the nature of its roots. The key is understanding the condition for real and equal roots.

Quadratic Equation Analysis

The given quadratic equation is:

$$kx^2 – 4x + 1 = 0$$

For a general quadratic equation of the form $ax^2 + bx + c = 0$, we can identify the coefficients:

  • $a = k$
  • $b = -4$
  • $c = 1$

Condition for Real and Equal Roots

A quadratic equation has real and equal roots when its discriminant is equal to zero. The discriminant ($D$) is calculated using the formula:

$$D = b^2 - 4ac$$

The condition for real and equal roots is:

$$D = 0$$

Solving for the Value of k

We substitute the coefficients ($a=k$, $b=-4$, $c=1$) into the discriminant formula and set it to zero:

  1. Substitute coefficients:

    $$(-4)^2 - 4(k)(1) = 0$$

  2. Simplify the equation:

    $$16 - 4k = 0$$

  3. Isolate the term with k:

    $$16 = 4k$$

  4. Solve for k:

    Divide both sides by 4:

    $$k = \frac{16}{4}$$

    $$k = 4$$

Therefore, the value of k that makes the roots of the quadratic equation $kx^2 – 4x + 1 = 0$ real and equal is 4.

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Important Questions from Quadratic equation

  1. Find the minimum value of 2x² – 5x – 3 and also find x.

  2. A quadratic equation $x^2 + 3x + k = 0$ has a discriminant equal to 9. What is the value of k?

  3. Reduce the equation $x^4 - 13x^2 + 36 = 0$ into a quadratic equation and find the roots of the reduced quadratic equation.
  4. If both roots of the quadratic equation, $x^2 + 3x + 2 = 0$, are also roots of another quadratic equation, $ax^2 + bx + c = 0$, then which of the following must be true?

  5. The nature of the roots of the quadratic equation $3x^{2} – 5x + 2 = 0$ is:
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