Question:
Value(s) of k for which the quadratic equation 2x2 -kx + k = 0 has equal roots is/are
(a) 0
(b) 4
(c) 8
(d) 0, 8
Solution:
(d)
Given equation is 2x2 – kx + k- 0
On comparing with ax2 + bx + c = 0, we get
a = 2, b= – k and c = k
For equal roots, the discriminant must be zero.
i.e., $D=b^{2}-4 a c=0$
$\Rightarrow \quad(-k)^{2}-4(2) k=0$
$\Rightarrow \quad k^{2}-8 k=0$
$\Rightarrow \quad k(k-8)=0$
$\therefore \quad k=0,8$
Hence, the required values of k are 0 and 8.