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Class 10 › Mathematics › Quadratic Equations
CBSE2026Class Class 10 · Mathematics1 Marks · Mcq✅ Verified
If the quadratic equation $9x^2+8kx+16=0$ has real and equal roots, then the value of $k$ is
A. $3$
B. $-3$
C. $-4$
D. $\dfrac{3}{2}$
✅ Answer & Solution
✅ Correct Answer: A
Step 1: For real and equal roots, discriminant $D=b^2-4ac=0$.
Step 2: Here $a=9,\ b=8k,\ c=16$:
$$(8k)^2-4(9)(16)=0$$
Step 3: $64k^2-576=0\Rightarrow 64k^2=576$
Step 4: $k^2=9\Rightarrow k=\pm 3$.
Step 5: From the given options, $k=3$.
Answer: (A) $3$
