Question

For what value of k, the equation `kx^2-6x2=0` has real roots?  

(a) `k≤-9/2`                     (b)`k≥-9/2` 

(c)` k≤-2`                         (d)  None of these 

Answer 1

(b) `k≥-9/2` 

It is given that the roots of the equation `(kx^2-6x-2=0)` are real 

∴` D≥0` 

⇒`(b^2-4ac)≥0` 

⇒`(-6)^2-4xxkxx(-2)≥0` 

⇒`36+8k≥0` 

⇒`k≥-36/8` 

⇒`k≥-9/2`