I try to solve the following problem but my answer does not correspond to the solution of the textbook. Please help me to understand the problem:

**The net force acting on a particle depends on the position of the particle along the x-axis according the relation F=F0+C*x, where F0=5N and C=-2N/m. The particle is initially at rest at x=0m when the force begins to act.**

a- Calculate the work done by the force when the particle reaches x values 1,2,3and 4 m?

b- Determine any positions ( besides x=0m ) where the work done is zero.

a- Calculate the work done by the force when the particle reaches x values 1,2,3and 4 m?

b- Determine any positions ( besides x=0m ) where the work done is zero.

I have problem for the question a.

What I did is to compute F1=F0+C*(1) [for x=1m]

that gives me F1=5-2=3N

So the work for F1 is W1= F1*(1)=3J

However the answer in the textbook it w1=

**4J**I dont know how they get that.

Thank you for your time.

B