Polynomials
RD Sharma
CBSE
Grade 10
Question:
If one zero of $3x^2 + 8x + k$ is reciprocal of the other, then $k$ is:
(a) $3$
(b) $-3$
(c) $\dfrac{1}{3}$
(d) $8$
Step-by-Step Solution
Key Concept: Zeroes $\alpha, 1/\alpha \Rightarrow \text{Product} = 1 \Rightarrow k/3 = 1 \Rightarrow k = 3$.
Product $= \alpha(1/\alpha) = 1 \Rightarrow k/3 = 1 \Rightarrow k = 3$. [1.0 Mark]
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🎯 Official CBSE Marking Scheme:
Setting product $= 1 \Rightarrow k = 3$: 1.0 Mark
Correct Answer: $3$
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