Q4 of 82 Page 4

If the quadratic equation px2 – 2√5 x + 15 = 0 has two equal roots then find the value of p. (CBSE 2015)

Cosnider px2 – 2√5 x + 15 = 0,


Here a = p , b = 2√5 p , c = 15


For real roots, D = 0


So,


b2 – 4ac = 0


(2√5 p)2 – 4p(15) = 0


20p2 – 60p = 0


20p(p – 3) = 0


p = 3, p = 0


But p = 0 is not possible.


∴ p = 3.

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