Addition of two different sized arrays

I have different sized arrays. First one is sized I=4000x4000, and the other ones are V1,V2=2000x2000. I want to sum them up. But I am having an error because their sizes are different. So I use;

RN=I+[V1;zeros(2000,2000)]/sqrt(6)+[V2;zeros(2000,2000)]/sqrt(2);

to make them equal size. But, I keep getting the same error wich;

Arrays have incompatible sizes for this operation.

And I want to make this operations in original;

RN=I+V1/sqrt(6)+V2/sqrt(2);
GN=I+V1/sqrt(6)-V2/sqrt(2);
BN=I-2*V1/sqrt(6);

How can I make these calculation?

Answer 1

[KSSV]

You may resize them to same size using imresize.

[Baris Demir]

Thanks. It woked.

[KSSV]

Thanks is accepting the asnwer. :)