Tính nhanh

X= 2/1x3 + 2/3x5 + 2/5x7 +....+ 2/77x79 + 2/79x81
Y= 1/1x3 + 1/3x5 + 1/5x7 +....+ 1/77x79 + 1/79x81
Z= 3/1x3 + 3/3x5 + 3/5x7 +....+ 3/77x79 + 3/77x81