Question

Tính tổng

P = 5.6.7+ 6.7.8 + 7.8.9 + ...+ 20.21.22

Answer 1

P = 5.6.7+ 6.7.8 + 7.8.9 + ...+ 20.21.22 = 50736 nha bạn . 

Answer 2

4P = 4.5.6.7+4.6.7.8+4.7.8.9+...+4.20.21.22

= 5.6.7.(8-4)+6.7.8.(9-5)+7.8.9.(10-6)+....+20.21.22.(23-19)

= 5.6.7.8-4.5.6.7+6.7.8.9-5.6.7.8+7.8.9.10-6.7.8.9+....+20.21.22-23-19.20.21.22

= 20.21.22.23-4.5.6.7 = 212520 - 840 = 211680

=> P = 52920

k mk nha