ở đâu vậy bạn?

Đặt \(A=\frac{25}{1\cdot6}+\frac{25}{6\cdot11}+\cdots+\frac{25}{25\cdot31}\)

\(A=5\cdot\left(\frac{5}{1\cdot6}+\frac{5}{6\cdot11}+\cdots+\frac{5}{26\cdot31}\right)\)

\(A=5\cdot\left(\frac11-\frac16+\frac16-\frac{1}{11}+\cdots+\frac{1}{26}-\frac{1}{31}\right)\)

\(A=5\cdot\left(\frac11-\frac{1}{31}\right)\)

\(A=5\cdot\frac{30}{31}\)

\(A=\frac{150}{31}\)

Vậy \(A=\frac{150}{31}\)

C.34

[sửa]

a. 8 921 x 4 + 8 921 + 7 - 8 921

= 8 921 x (4 + 7 - 1)

= 8 921 x 10

= 89 210

b. 22 775 - 823 + 3 832 + 2 225

= (22 775 + 2 225) + (3 832 - 823)

= 25 000 + 3 009

= 28 009

a. 8 921 x 4 + 8 921 + 7 - 8 921

= 8 921 x (4 + 7 - 1)

= 8 921 x 1

= 89 210

b. 22 775 - 823 + 3 832 + 2 225

= (22 775 + 2 225) + (3 832 - 823)

= 25 000 + 3 009

= 28 009

\(\left(\frac15^{}\right)^5\cdot5^5=\frac{1}{5^5}\cdot5^5=\frac{5^5}{5^5}=1\)

I like rice and chicken. I’d like an orange. I am full, so I wouldn’t

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