Question

tính 1.2.3.4+2.3.4.5+.....+97.98.99.100

Answer 1

Đặt A=1.2.3.4+2.3.4.5+...+97.98.99.100

4A=(1.2.3+2.3.4+3.4.5+4.5.6+...+98.99.100)4

4A=1.2.3(4-0)+2.3.4(5-1)+3.4.5(6-2)+4.5.6(7-3)+...+98.99.100(101-97)

4A=1.2.3.4+2.3.4.5-1.2.3.4+3.4.5.6-2.3.4.5+4.5.6.7-3.4.5.6+...+98.99.100.101-97.98.99.100

4A=1.2.3.4-1.2.3.4+2.3.4.5-2.3.4.5+3.4.5.6-3.4.5.6+...+97.98.99.100-97.98.99.100+98.99.100.101

4A=98.99.100.101

A=98.99.100.101/4 

 

Answer 2

5A=(5-0).1.2.3.4+(6-1).2.3.4.5+...+(101-96).97.98.99.100

5A=1.2.3.4.5-0+2.3.4.5.6-1.2.3.4.5+...+97.98.99.100.101-96.97.98.99.100

5A=97.98.99.100.101=9505049400

A=1901009880

Answer 3

Nguyen Quang Trung sai

Answer 4

uk, sai thì làm đi

Answer 5

t làm như Cam Hai Dang đó