262yes , my fault.
if the range of tan-1 (3x2 + bx + c) is [0,pi/2) then relate b and c.
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7 Answers
2620 ≤ tan-1(x) < pi/2 for x→[0,∞)
thus ,
0 ≤ 3x2 +bx +c < ∞
Discriminant ≤0
b2-12c ≤ 0
36why is discriminant less than 0
i guess only equal to 0
and so its b2 = 12c and not b2 - 1c < 0....
36yes, the parabola is upward opening and touches the axis......
and, if ax2 + bx + c > 0 and a > 0 then D = 0
if the case would have been,
ax2 + bx + c > 0 and a > 0 then one could say D > 0
there's no such case like D > 0
