Mathematics
If the quadratic equation, px2 - px + 15 = 0 has two equal roots, then the value of p is:
0
3
6
both 0 and 3
Quadratic Equations
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Answer
Comparing px2 - px + 15 = 0 with ax2 + bx + c = 0 we get,
a = p, b = p and c = 15.
We know that,
Since equations has equal roots,
⇒ D = 0
⇒ b2 - 4ac = 0
⇒ ( p)2 - 4(p)(15) = 0
⇒ 20p2 - 60p = 0
⇒ 20p(p - 3) = 0
⇒ 20p = 0 or (p - 3) = 0 [Using Zero-product rule]
⇒ p = 0 or p = 3.
Since p = 0 would make the equation no longer quadratic, we take:
p = 3
Hence, option 2 is the correct option.
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