Expand each of the following using suitable identities: (i) (x+2y+4z)^2 (ii) (2x-y+z)^2 (iii) (-2x+3y+2z)^2 (iv) (3a-7b-c)^2 (v) (-2x+5y-3z)^2 (vi) \left[\frac{1}{4}a-\frac{1}{2}b+1\right]^2