If f(x)=ax2+bx+c, where a≠0,b,c∈R, then which of the following conditions implies that f(x) has real roots?

(1) If f(1)=0⇒a+b+c=0So, roots are real.(2) D=b2−4acIf ac<0⇒D>0So, roots are real.(3) 4ac−b2<0⇒b2−4ac>0So, roots are real.(4) This is not the sufficient condition.