Q.

If the roots of equation ax2+bx+c=0, a0 are real and equal, then which of the following relation is true

1 a=b2c    
2 b2=ac    
3 ac=b24    
4 c=b2a  

Ans.

(3)

If the discriminant is equal to zero, i.e., b2-4ac=0 where a, b, c are real numbers and a0, then roots of the quadratic equation ax2+bx+c=0, are real and equal b2-4ac=0ac=b24