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Question

Which of the following is a quadratic equation?

This question was previously asked in
RRB ALP/Technician 2018 CBT 2 Electronics Mechanic Question Paper (23-Jan-2019) (Shift 1)
The correct answer is
$5x^2+4-7x$

Understanding Quadratic Equations

A quadratic equation is a polynomial equation where the highest power (degree) of the variable is 2. The standard form is \(ax^2 + bx + c = 0\), where \(a \neq 0\). We need to find the option where the variable '\(x\)' has a maximum exponent of 2.

Analyzing the Options

Let's examine each option to determine the highest power of '\(x\)':

  • Option 1: \(x^2+3x^3+5\)

    The highest power of '\(x\)' is 3 (from the term \(3x^3\)). This is a cubic equation, not quadratic.

  • Option 2: \(x^{3/5}+y^2-3\)

    This equation contains a fractional exponent (\(x^{3/5}\)). Quadratic equations must have integer exponents, specifically a highest exponent of 2.

  • Option 3: \(5x^2+4-7x\)

    The terms are \(5x^2\), $4$ (which is \(4x^0\)), and \(-7x\) (which is \(-7x^1\)). The highest power of '\(x\)' is 2. This equation can be written in standard form as \(5x^2 - 7x + 4 = 0\). Therefore, this is a quadratic equation.

  • Option 4: \(x^2-2x^{1/5}+2\)

    This equation includes a fractional exponent (\(x^{1/5}\)), disqualifying it as a quadratic equation.

  • Option 5:

    This option is empty and cannot be evaluated.

Identifying the Quadratic Equation

Based on the analysis, the only equation that meets the definition of a quadratic equation (highest power of \(x\) is 2) is Option 3.

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Similar Questions

  1. Find the zeros of the function \(f(x) = (x - 17)(x - 7)\)
  2. Find the roots of the following equation
    $x^2 + 12x - 36 = 0$
  3. Which of the following equations are quadratic equations?
    I) $x^2 + 4x + 23 = x + \frac{33}{28}$
    II) $\frac{2}{3}x^2 + 6x + 2 = x^2 + 8$
    III) $6x^2 + 4x + 18 = 6x^2 - 6x$
  4. Find the roots of the following equation:
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  5. Sum of the zeros of the equation \(3x^2+2x-5\) is?
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  7. If $12x^2 - ax + 7 = ax^2 + 9x + 3$ has only one (repeated) solution, then the positive integral solution of $a$ is:
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Important Questions from Quadratic Equations

  1. Find the zeros of the function \(f(x) = (x - 17)(x - 7)\)
  2. Find the roots of the following equation
    $x^2 + 12x - 36 = 0$
  3. Which of the following equations are quadratic equations?
    I) $x^2 + 4x + 23 = x + \frac{33}{28}$
    II) $\frac{2}{3}x^2 + 6x + 2 = x^2 + 8$
    III) $6x^2 + 4x + 18 = 6x^2 - 6x$
  4. Find the roots of the following equation:
    $4x^2 + 4x - 3 = 0$
  5. Sum of the zeros of the equation \(3x^2+2x-5\) is?
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