Question

1/4.7+1/7.10+1/10.13+...+1/73/76

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Answer 1

nhớ k nha

1/4.7+1/7.10+...+1/73.76=1/3.(3/4.7+3/7.10+..+3/73.76)

=1/3.(1/4-1/7+1/7-1/10+1/10-......+1/73-1/76)

=1/3.(1/4-1/76)

=1/3.9/38=3/38

nhớ k nha

Answer 2

\(=\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{73}-\frac{1}{76}\)

\(=\frac{1}{4}-\frac{1}{76}\)

\(=\frac{9}{38}\)

Answer 3

\(\frac{9}{38}\)

Answer 4

\(\frac{9}{38}\)