Question

C=1x2x3+2x3x4+...+48x49x50

giải nhanh giúp mik vs

Answer 1

\(C=1.2.3+2.3.4+........+48.49.50\)

\(\Rightarrow4C=1.2.3.4+2.3.4.4+........+48.49.50.4\)

\(=1.2.3.4+2.3.4.\left(5-1\right)+.........+48.49.50.\left(51-47\right)\)

\(=1.2.3.4+2.3.4.5-1.2.3.4+........+48.49.50.51-47.48.49.50\)

\(=48.49.50.51\)

\(\Rightarrow C=\frac{48.49.50.51}{4}=1499400\)

Answer 2

Ta có C = 1 x 2 x 3 + 2 x 3 x 4 + ... + 48 x 49 x 50

=>   4C  = 1 x 2 x 3 x 4 + 2 x 3 x 4 x 4 + ....  + 48 x 49 x 50 x 4

       4C   = 1 x 2 x 3 x 4 +  2 x 3 x 4 x (5 - 1)+ ... + 48 x 49 x 50 x (51 - 47)

       4C   = 1 x 2 x 3 x 4 + 2 x 3 x 4 x 5 - 1 x 2 x 3 x 4 + .... + 48 x 49 x 50 x 51 -  47 x 48 x 49 x 50 

       4C   = 48 x 49 x 50 x 51

       4C   = 5997600

         C   = 5997600 : 4

         C   = 1499400

Vậy C   = 1499400

Answer 3

C = 1x2x3+2x3x4+...+48x49x50

4C = 1x2x3x4+2x3x4x4+...+48x49x50

4C = 1x2x3x(4-0)+2x3x4x(5-1)+...+48x49x50x(51-47)

4C = 1x2x3x4-0x1x2x3+2x3x4x5-1x2x3x4+...+48x49x50x51-47x48x49x50

4C = 48x49x50x51

=> C = (48x49x50x51)/4

C = 12x49x50x51

Answer 4

                                     Bài làm :

\(C=1.2.3+2.3.4+........+48.49.50\)

\(\Rightarrow4C=1.2.3.4+2.3.4.4+........+48.49.50.4\)

\(=1.2.3.4+2.3.4.\left(5-1\right)+.........+48.49.50.\left(51-47\right)\)

\(=1.2.3.4+2.3.4.5-1.2.3.4+........+48.49.50.51-47.48.49.50\)

\(=48.49.50.51\)

\(\Rightarrow C=\frac{48.49.50.51}{4}=1499400\)

Vậy C=1499400

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