If the roots of the equation `x^2+2a x+b=0` are real and distinct and they differ by at most `2m` ,then `b` lies in the interval a.`(a^2,a^2,+m^2)` b. `(a^2-m^2, a 62)` c. `[a^2-m^2, a^2)` d. none of these