Given:
• The equation 9y² + 6ky + 4= 0 has equal roots .
To find :
• The value of k.
Solution:
• As we know that , For equal roots :
• Discriminant must be equal to zero.
D = b²- 4ac = 0
Here ,
a= 9 , b = 6k , and c = 4 .
=> b²-4ac= 0
=> (6k)² - 4 (9)(4)=0
=> 36k² - 144=0
=> 36k²= 144
=> k²= 144/36
=> k²= 4
=> k = ±2.
Hence ,the option b is correct .
I hope it will help you.
Regards.