Question

If the quadratic equation px\frac{1}{2} – 2 px + 15 = 0 has two equal roots, then find the value of p.

Answer 1

If in equation ax

2

+bx+c=0 the two roots are equal

Then b

2

−4ac=0

In equation px

2

−2

5

px+15=0

a=p,b=−2

5

p and c=15

Then b

2

−4ac=0

⇒(−2

5

p)

2

−4×p×15=0

⇒20p

2

−60p=0

⇒20p(p−3)=0

So when p−3=0⇒p=3

p



=0 as it makes coefficient of x

2

=0

Hence, p=3