Electric field #vecE# is the gradient of potential #V# and is written as

#vecE=-grad V#

In vector form it can be expressed as

#vecE=-(hati(del)/(delx)+hatj(del)/(dely)+hatk(
del)/(delz))V# ......(1)

It is given that Electric Potential at any point #(x,y,z)# is

#V=3x^2#

As the given function of Potential #V# is independent of #y and z#, in the equation (1) derivative with respect to #y and z# terms vanish. (1) reduces to

#vecE=-hati(delV)/(delx)#

Inserting values of #V#, we get

#vecE=-hati(del(3x^2))/(delx)#

or #vecE=-6xhat i# .....(2)

To find the electric field at the desired point #(2,0,1)#, inserting #x=2# in (2) above, (distance in #m#)

#vecE=-(6xx2)hat i=-12hati Vm^-1#

assuming electric potential function is given in Volt