Question

1:Tính

a,        7+6.(\(-\frac{1}{2}\))\(^2\)

b,        \(\frac{2^5.7+2^5}{2^5.5^2-2^5.3}\)

a,        A=\(\frac{-1}{20}+\frac{-1}{30}+\frac{-1}{42}+\frac{-1}{56}+\frac{-1}{72}+\frac{-1}{90}\)

Answer 1

Câu a, b phân k ra là ok 

\(c)\) \(A=\frac{-1}{20}+\frac{-1}{30}+\frac{-1}{42}+\frac{-1}{56}+\frac{-1}{72}+\frac{-1}{90}\)

\(A=\left(-1\right)\left(\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}\right)\)

\(A=\left(-1\right)\left(\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}\right)\)

\(A=\left(-1\right)\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\right)\)

\(A=\left(-1\right)\left(\frac{1}{4}-\frac{1}{10}\right)\)

\(A=\left(-1\right).\frac{3}{20}\)

\(A=\frac{-3}{20}\)

Vậy \(A=\frac{-3}{20}\)

Chúc bạn học tốt ~ 

Answer 2

cảm ơn bạn nhiều nha

Answer 3

Thôi gợi ý câu b) 

\(b)\) \(\frac{2^5.7+2^5}{2^5.5^2-2^5.3}\)

\(=\)\(\frac{2^5\left(7+1\right)}{2^5\left(5^2-3\right)}\)

\(=\)\(\frac{7+1}{25-3}\)

\(=\)\(\frac{8}{22}\)

\(=\)\(\frac{4}{11}\)

Chúc bạn học tốt ~ 

Answer 4

\(A=\frac{-3}{20}\)

Chúc bạn học tốt\(\approx\)