Môn Toán Lớp 6: A=1/1.3 1/3.5 1/5.7 ...1/47.49 1/49.51 1/1.4 1/4.7 1/7.10 ...1/94.971/97.100

Question

Môn Toán Lớp 6:  A=1/1.3 + 1/3.5 + 1/5.7 +...+1/47.49 + 1/49.51 1/1.4 + 1/4.7 +1/7.10 +...+1/94.97+1/97.100

dinhcongson · Answer

A = 1/{1.3} + 1/{3.5} + 1/{5.7} + ... + 1/{47.49} + 1/{49.51}   A = 1/2. ( 2/{1.3} + 2/{3.5} + 2/{5.7} + ... + 2/{47.49} + 2/{49.51} )   A = 1/2. ( 1 - 1/3 + 1/3 - 1/5 + 1/5 - 1/7 + ... + 1/47 - 1/49 + 1/49 - 1/51 )   A = 1/2.  ( 1 - 1/51 )   A = 1/2. 50/51   A = 25/51   $ text{ __________________________________________________________ }$   1/{1.4} + 1/{4.7} + 1/{7.10} + ... + 1/{94.97} + 1/{97.100}   = 1/3. ( 3/{1.4} + 3/{4.7} + 3/{7.10} + ... + 3/{94.97} + 3/{97.100} )   = 1/3. ( 1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + ... + 1/94 - 1/97 + 1/97 - 1/100 )   = 1/3. ( 1 - 1/100 )   = 1/3. 99/100   = 33/100

tonhitruc · Answer

a) A = 1/(1.3) + 1/(3.5) + 1/(5.7) + ... + 1/(49.51)     2A = 2/(1.3) + 2/(3.5) + 2/(5.7) + ... + 2/(49.51)     2A = 1/1 - 1/3 + 1/3 - 1/5 + 1/5 - 1/7 + ... + 1/49 - 1/51     2A = 1 - 1/51     2A = 50/51     A = 50/51 : 2     A =25/51   b) Đặt:   B = 1/(1.4) + 1/(4.7) + 1/(7.10) + ... + 1/(94.97) + 1/(97.100)   3B = 3/(1.4) + 3/(4.7) + 3/(7.10) + ... + 3/(94 . 97) + 3/(97.100)   3B = 1/1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + ... + 1/94 - 1/97 + 1/97 - 1/100   3B = 1 - 1/100   3B = 99/100   B = 99/100 : 3   B = 33/100

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Môn Toán Lớp 6: A=1/1.3 + 1/3.5 + 1/5.7 +…+1/47.49 + 1/49.51 1/1.4 + 1/4.7 +1/7.10 +…+1/94.97+1/97.100

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