Question

Tính a

A=1.2+2.3+3.4+......+49+50=?????

Giúp mình nha mình tick cho

Answer 1

có lỗi ko

Answer 2

Ta có : A = 1.2 + 2.3 + 3.4 + ..... + 49.50

=> 3A = 1.2.3 - 1.2.3 + 2.3.4 - 2.3.4 + .... + 49.50.51

=> 3A = 49.50.51

= >A = 49.50.51/3 = 41650

Answer 3

3A= 1.2.3 + 2.3.(4-1) +3.4.(5-2) +...+ 99.100.(101-98)

3A= 1.2.3 + 2.3.4 - 1.2.3 + 3.4.5 - 2.3.4 +...+-99.100.98

3A=99.100.101

A= 33.100.101

Answer 4

A= 1.2+2.3+3.4+...+48.49+49.50

3A= 1.2.3+2.3.3+3.4.3+...+48.49.3+49.50.3

3A=1.2.3+ 2.3.(4-1)+3.4.(5-2)+...+48.49.(50-47)+ 49.50.(51-48)

3A=1.2.3+ 2.3.4- 1.2.3+ 3.4.5- 2.3.4+...+ 48.49.50- 47.48.49 + 49.50.51 - 49.50.48

3A=49.50.51

A=( 49.50.51 ) /3 = 41650