The number of solutions of the equation x3 + x2 + 4x + 2sinx = 0 in 0 ≤ x ≤ 2π
1
x3 + (x+2)2 + 2sinx = 4
Clearly x = 0 satisfies the equations
If 0 < x ≤ π, x3 + (x+2)2 + 2sinx > 4
If π < x ≤ 2π, x3 + (x+2)2 + 2sinx > 27 + 25 - 2
So x = 0 is the only solution.