MonotonicityHard
Question
If f(x) = x2 + kx + 1 is monotonic increasing in [1 , 2] then the minimum values of k is-
Options
A.4
B.-4
C.2
D.-2
Solution
f(x) = x2 + kx + 1
f′(x) =
(x2 + kx + 1) > 0 = 2x + k > 0
k > - 2x x ∈ [1, 2] k > -2
f′(x) =
(x2 + kx + 1) > 0 = 2x + k > 0k > - 2x x ∈ [1, 2] k > -2
Create a free account to view solution
View Solution FreeMore Monotonicity Questions
f(x) = 2x − tan−1 x − log (x + ) is monotonic increasing when...If x ∈ (0, 1) then f(x) = x100 + sin x - 1 is-...The length of largest continuous interval in which function f (x) = 4x - tan2x is monotonic, is -...If f(x) = x5 − 20x3 + 240 x, then f(x) is...If a < 0, the function f(x) = eax + e-ax is monotonically decreasing for all values of x, where-...