Polynomials
RD Sharma
CBSE
Grade 10
Question:
If one zero of the quadratic polynomial $x^2 + 3x + k$ is $2$, then the value of $k$ is:
(a) $10$
(b) $-10$
(c) $-7$
(d) $-2$
Step-by-Step Solution
Key Concept: If $x = 2$ is a zero, $p(2) = 0 \Rightarrow 2^2 + 3(2) + k = 0$.
$2^2 + 3(2) + k = 0 \Rightarrow 4 + 6 + k = 0 \Rightarrow k = -10$. [1.0 Mark]
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🎯 Official CBSE Marking Scheme:
Substituting $x = 2$ and solving for $k = -10$: 1.0 Mark
Correct Answer: $-10$
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