Solving a complicated equation in matlab

I am trying to solve this equation in Matlab, I need to find the negative solution of this euation, here is what I do. syms x >> f=inline(cosh(3.7*x)+2.2*x^2-5*x-4); >> fzero(f,-2)

ans =

-0.351409329825233

I dont know what I am doing wrong?

Any help appreciated.

Answer 1

[Carlos]

I think there is nothing wrong with your code. If I do

f(-0.351409329825233)

the answer is

ans =

   -3.9968e-015

So -0.351409329825233 is a negative root of your equation.

Answer 2

[shelly]

Thank you