Question

find the value of q so that the quadratic eq. qx(x-3)+9=0 has two equal roots.

Answer 1

Here,
qx^2 -3qx+9 = 0
We know , if D =0 i.e b^2 -4ac = 0 , then the quadratic equation has equal roots.
So,
(-3q)^2 -4*q*9 = 0
9q^2 -36q = 0
q^2 -4q = 0
q(q-4)= 0
Either q= 0 or q= 4.
q can't be zero so the value of q will be 4.