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Question

If the equation \(2x^2 + kx + 1.25k = 0\) has repeated roots, then the value of \(k\) will be:

This question was previously asked in
RRB Group D 2018 Question Paper (11-Oct-2018) (Shift 3)
The correct answer is

\(k = 10 \text{ or } k = 0\)

A quadratic \(ax^2 + bx + c = 0\) has repeated (equal) roots when its discriminant \(b^2 - 4ac = 0\).

Here \(a = 2\), \(b = k\) and \(c = 1.25k\), so discriminant \(= k^2 - 4 \times 2 \times 1.25k = k^2 - 10k\).

Setting \(k^2 - 10k = 0\) gives \(k(k - 10) = 0\).

Therefore \(k = 0\) or \(k = 10\).

Hence, \(k = 10 \text{ or } k = 0\).

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Important Questions from Quadratic Equation

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