Maths-
General
Easy
Question
The number of solutions of the equation x3 + 2x2 + 5x + 2 cos x = 0 in [0, 2
] is :
- 0
- 1
- 2
- 3
The correct answer is: 3
Let f(x) = x3 + 2x2 + 5x + 2 cos x
Þ
= 3x2 + 4x + 5 − 2 sin x
Now 
[
−1 ≤ x ≤ 1]
Þ
f(x) is an increasing function.
Nowf(0) = 2
f(x) = 0 has no solution in [0, 2p]
Hence (a) is correct.
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