Question

1) tinh nhanh

a) 85.127+5.127.3

b) 1/2 + 5/6 + 11/2 +19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90

3) tinh gia tri bieu thuc 

a) A= 2^2 + 4^2 + 6^2+ ...+ 20^2

b) B= 1^2 + 2^2 + 3^2 +...+ 10^2

Answer 1

a) 85 . 127 + 5 . 127 . 3

= (85 + 15) . 127

= 100 . 127

= 12700

Answer 2

a) 85 . 127 + 5 . 127 . 3

= (85 + 15) . 127

= 100 . 127

= 12700

b) 1/2 + 5/6 + 11/12 +19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90

1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10

1-1/10

9/10