\(A=\frac{1}{2}+\frac{1}{14}+\frac{1}{35}+\frac{1}{65}+\frac{1}{104}+\frac{1}{152}=>\frac{1}{2}A=\frac{1}{4}+\frac{1}{28}+\frac{1}{70}+...+\frac{1}{304}\)

                                                                                                   \(=\frac{1}{1.4}+\frac{1}{4.7}+\frac{1}{7.10}+...+\frac{1}{16.19}=\frac{1}{3}.\left(\frac{3}{1.4}+\frac{3}{4.7}+...+\frac{3}{16.19}\right)=\frac{1}{3}.\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+...+\frac{1}{16}-\frac{1}{19}\right)=\frac{1}{3}.\left(1-\frac{1}{19}\right)=\frac{1}{3}.\frac{18}{19}=\frac{6}{19}\)=> A= \(\frac{6}{19}:\frac{1}{2}=\frac{12}{19}\)

đúng nha

A=2/4+2/28+2/70+2/130+2/208+2/304

A=2/1.4+2/4.7+2/7.10+2/10.13+2/13.16+2/16.19

A=2/3.(1-1/4+1/4-1/7+...+1/16-1/19)

A=2/3.(1-1/19)

A=2/3.18/19

A=12/19

Cách này nhanh hơn nhưng vẫn đúng bạn ạ

\(=49\times\left(55+48-3\right)=49\times100=4900\)

    7 3 + − 5 6 + − 2 3 = 7 3 + − 5 6 + − 2 3 = 7 3 + − 2 3 + − 5 6 = 5 3 + − 5 6 = 10 + − 5 6 = 5 6

    4 3 − − 11 6 − 2 9 + 5 3 = 4 3 + 11 6 + 2 9 + 5 3 = 4 3 + 11 6 + 2 9 + 5 3 = 24 + 33 + 4 + 33 18 = 91 18

     5 − 7 − − 5 − 7 + 4 3 = − 5 7 − 5 7 + 4 3 = − 10 7 + 4 3 = − 30 + 28 21 = − 2 21

-359+181-123+350-172=0-123=-123

chúc bạn học tốt!

Ko bt làm

   4,25.58,47-125+41,53.4,25

= 4,25.58,47+41,53.4,25-125

= 4,25.(58,47+41,53)-125

= 425-125

= 300

4,25.58,47-125+41,53.4,25

=4,25.(58,47+41,53)-125

=4,25.100-125

=425-125=300

4,25.58,47-125+41,53.4,25

=4,25.58,47+41,53.4,25-125

=4,25(58,47+41,53)-125

=4,25.100-125

=425-125

=300

8 − 9 4 + 2 7 − − 6 − 3 7 + 5 4 − 3 + 2 4 − 9 7 = 8 − 9 4 + 2 7 + 6 + 3 7 − 5 4 − 3 − 2 4 + 9 7 = 8 + 6 − 3 − 9 4 − 5 4 − 2 4 + 2 7 + 3 7 + 9 7 = 11 − 4 + 2 = 9

  234456

-

  123798

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   110658

ĐÂY NHÉ !!! ĐÚNG CHO MK LIKE NHEN !!!