If a,b∈Rand ax2 +bx +6=0,a≠0 does not have distinct real roots, the

Here, D ≤ 0and f(x)≥0,∀x∈R∴f(3)≥0⇒9a+3b+6≥0 or 3a+b≥−2Minimum value of 3a + b is - 2.and f(6) ≥036a +6b+6≥06a + b ≥ -1Minimum value of 6a + b is -1.