please explain clearly

3. (25 points) Consider the function 7 : R3 - R3 defined by T(r, y, z) = (3x, x - y, 2x + y + 2). (i) Prove that T is a linear transformation. (ii) Find the representing matrix of T relative to the basis B = {01 = (1,0,0), 02 = (1, 1, 0), 03 = (1, 1, 1) } of 13