Bài 1 và 4:21064

Bài 2:41/5; 42/5; 43/5; 44/5; 45/5

Bài 3:10 xe

1+2+3+4+5+6+7+8+9+10 = 55

1+2+3+4+5+6+7+8+9+10=55

\(a,\frac{6}{7}+\frac{5}{8}:5-\frac{3}{16}\cdot(-2)^2\)

\(=\frac{6}{7}+\frac{5}{8}:\frac{5}{1}-\frac{3}{16}\cdot4\)

\(=\frac{6}{7}+\frac{5}{8}\cdot\frac{1}{5}-\frac{3}{16}\cdot4\)

\(=\frac{6}{7}+\frac{1}{8}-\frac{3\cdot4}{16}\)

\(=\frac{6}{7}+\frac{1}{8}-\frac{3\cdot1}{4}\)

\(=\frac{6}{7}+\frac{1}{8}-\frac{3}{4}=\frac{48+7-42}{56}=\frac{13}{56}\)

\(b,\frac{2}{3}+\frac{1}{3}\cdot\left[\frac{-2}{3}+\frac{5}{6}\right]:\frac{2}{3}\)

\(=\frac{2}{3}+\frac{1}{3}\cdot\left[\frac{-4+5}{6}\right]:\frac{2}{3}\)

\(=\frac{2}{3}+\frac{1}{3}\cdot\frac{1}{6}:\frac{2}{3}=\frac{2}{3}+\frac{1}{3}\cdot\frac{1}{6}\cdot\frac{3}{2}=\frac{2}{3}+\frac{1}{12}=\frac{8}{12}+\frac{1}{12}=\frac{9}{12}=\frac{3}{4}\)

c, Xem lại đề

d, \(\frac{-3}{5}+\left[\frac{-2}{5}-99\right]\)

\(=\frac{-3}{5}+\frac{-497}{5}=\frac{-500}{5}=-100\)

b, Tìm x

\(\left[\frac{2}{11}+\frac{1}{3}\right]\cdot x=\left[\frac{1}{7}-\frac{1}{8}\right]\cdot56\)

\(\Rightarrow\left[\frac{2}{11}+\frac{1}{3}\right]\cdot x=\left[\frac{8}{56}-\frac{7}{56}\right]\cdot56\)

\(\Rightarrow\left[\frac{6}{33}+\frac{11}{33}\right]\cdot x=1\)

\(\Rightarrow\frac{17}{33}\cdot x=1\)

\(\Rightarrow x=1:\frac{17}{33}=1\cdot\frac{33}{17}=\frac{33}{17}\)

thank ^_^

Program HOC24;

uses crt;

var s: real;

i,n,j,l: integer;

begin

clrscr;

s:=2014;

for i:= 1 to 2012 do

for j:= 4 to 2015 do

for l:=2 to 2013 do

s:=s+(i*j)/(l*(l+1));

write('S = ',s:6:2);

Readln;

end.

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