Question

Tính S biết: S=1.2+2.3+3.4+4.5+................+49.50

 

 

 

 

 

Answer 1

3.s =1.2.3+2.3.3 +3.4.3+........+49.50

3s= 1.2 .3+ 2.3.(4-1) +.....+ 49.50( 51-48)

3s=49.50.51

3s=124950

s= 124950chia 3

s= 41650

Answer 2

chia=/ or chia= :

Answer 3

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Answer 4

Ta có:

  S=1.2+2.3+3.4+4.5+...+49.50

3S=1.2.3+2.3.3+3.4.3+4.5.3+...+49.50.3

3S=1.2.3+2.3.(4-1)+3.4.(5-2)+...+49.50.(51-48)

3S=1..2.3+2.3.4-1.2.3+3.4.5-2.3.4+...+49.50.51-48.49.50

3S=49.50.51

S=49.50.51:3

S=41650