Question

1.Thực hiện phép tính:

a) 45 : \(2\frac{4}{7}+50\)^o/_o - 1,25

b) \(4\frac{2}{5}.0,5-1\frac{3}{7}.14\)^o/_o + (-0,8)

c) \(1\frac{3}{8}+\frac{1}{8}:\)(75^o/_o - \(\frac{1}{2}\)) - 25^o/_o . \(\frac{1}{2}\)

d) 75^o/_o + 18 + 1,25 . \(\frac{4}{5}-18\frac{3}{4}\)

2.THPT:

A = \(\frac{9}{1.2}+\frac{9}{2.3}+\frac{9}{3.4}+...+\frac{9}{98.99}+\frac{9}{99.100}\)

B = \(\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}+...+\frac{2}{93.95}\)

C = \(\left(1-\frac{1000}{2017}\right).\left(1-\frac{1001}{2017}\right)...\left(1-\frac{2017}{2018}\right)\)

D = \(\frac{5}{2.7}+\frac{4}{7.11}+\frac{3}{11.14}+\frac{1}{14.15}+\frac{13}{15.28}\)

3. Tìm x:

a)\(\left(2\frac{4}{5}x-50\right):\frac{2}{3}=51\)

b) \(3\frac{1}{3}x+16\frac{3}{4}=-13,25\)

c) \(\frac{2}{3}x-\frac{5}{6}x=\frac{11}{24}\)

d) x + \(\frac{2}{5}x=\frac{-14}{55}\)

e) \(\frac{2}{5}x-x=\frac{\left(-2018\right)^0}{5^2}\)

f) x + \(\left(x+\frac{2}{7}\right)+\frac{-5}{11}=\frac{4}{11}\)

Help me!!!!!!

Answer 1

\(2.THPT\)

\(A=\frac{9}{1.2}+\frac{9}{2.3}+\frac{9}{3.4}+...+\frac{9}{98.99}+\frac{9}{99.100}\)

\(A=9\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}\right)\)

\(A=9\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{99}-\frac{1}{100}\right)\)

\(A=9\left(1-\frac{1}{100}\right)\)

\(A=9.\frac{99}{100}\)

\(A=\frac{891}{100}\)

\(B=\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}+...+\frac{2}{93.95}\)

\(B=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+...+\frac{1}{93}-\frac{1}{95}\)

\(B=\frac{1}{5}-\frac{1}{95}\)

\(B=\frac{18}{95}\)

\(D=\frac{5}{2.7}+\frac{4}{7.11}+\frac{3}{11.14}+\frac{1}{14.15}+\frac{13}{15.28}\)

\(D=\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{15}+\frac{1}{15}-\frac{1}{28}\)

\(D=\frac{1}{2}-\frac{1}{28}\)

\(D=\frac{13}{28}\)