Electric field as a function, find potential diff

1. The problem statement, all variables and given/known data
the electric field between two conducting surfaces is given by an expression:

E(x) = 9x^2 <i hat> where x is any location between the conductors. if one conductor is at x = 1 meter and the other is at x = 3 meter, what is the potential difference between them


2. Relevant equations

electric potential difference deltaV = V_B - V_A = - [<integral> E*dx] where x is distance

3. The attempt at a solution

i'm guessing i am supposed to do do the integral with the limits being from x = 1 to x = 3 so:
deltaV = [9x^3/3]x from x = 1 to x = 3, so ((9*27)/3)*3 - (9/3)*1 = 243 - 3 = +240 volts

i am not too sure about the correctness of my integration, but even still, was my approach correct?

thanks

 

i thought my integration was wrong, i had it the way you have before, but doubted myself, well i redid the intrgral and did the calculation:

deltaV = [9x^3/3] from x = 1 to x = 3, so ((9*27)/3) - (9/3) = 81 - 3 = 78 volts

correct now?
thanks