Quadratic Equations
RD Sharma
CBSE
Grade 10
Question:
Values of $k$ for which the quadratic equation $2x^2 - k x + k = 0$ has equal roots is/are:
(a) $0$ only
(b) $4$
(c) $8$ only
(d) $0, 8$
Step-by-Step Solution
Key Concept: Equal roots $\Rightarrow D = b^2 - 4ac = 0 \Rightarrow (-k)^2 - 4(2)(k) = 0 \Rightarrow k^2 - 8k = 0 \Rightarrow k(k - 8) = 0 \Rightarrow k = 0$ or $k = 8$.
$k^2 - 8k = 0 \Rightarrow k(k - 8) = 0 \Rightarrow k = 0$ or $k = 8$. [1.0 Mark]
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🎯 Official CBSE Marking Scheme:
Setting $D = 0$ and solving $k = 0, 8$: 1.0 Mark
Correct Answer: $0, 8$
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