a) Ta có:
252/x = 84/97
==> x.84=252.97
==> x.84= 24444
==> x=24444:84
==> x=291
b) x/17 + 19/34=1/2
X/17=1/2–19/34
X/17=17/34–19/34
X/17=—2/34
==> x.34=17.(—2)
==> x.34=-34
==> x=(—34):34
==> x=—1
a \(\frac{252}{x}\)\(=\)\(\frac{84}{97}\)
b \(\frac{4}{5}\)\(-\)\(\frac{7}{5}\)\(:\)\(x\)\(=\)\(\frac{1}{6}\)
c \(\frac{50}{19}\)\(\cdot\)\(\frac{38}{25}\)\(< \)\(x\)\(< \)\(\frac{69}{17}\)\(+\)\(\frac{33}{17}\)
a) \(5\frac{8}{17}\div x+\frac{-1}{17}\div x+3\frac{1}{17}\div17\frac{1}{3}=\frac{4}{17}\)
b)\(\frac{1}{1\times4}+\frac{1}{4\times7}+\frac{1}{7\times10}+...+\frac{1}{x\times\left(x+3\right)}=\frac{6}{19}\)
1(\(\left(\frac{4}{286}-\frac{2}{7\times9}\right)\left(\frac{4}{286}-\frac{2}{9\times11}\right)......\left(\frac{4}{286}-\frac{2}{97\times99}\right)\)
2)\(A=\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{19}+\frac{1}{20}}{\frac{19}{1}+\frac{18}{2}+\frac{17}{3}+...+\frac{2}{18}+\frac{1}{19}}\)
\(\frac{\frac{1}{19}+\frac{2}{18}+\frac{3}{17}+...+\frac{18}{2}+\frac{19}{1}}{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{19}+\frac{1}{20}}\)\(\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{99}+\frac{1}{100}}{\frac{99}{1}+\frac{98}{2}+\frac{97}{3}+...+\frac{2}{98}+\frac{1}{99}}\)
Tính:
a) \(A=\frac{(1+17)(1+\frac{17}{2})(1+\frac{17}{3})...(1+\frac{17}{19})}{(1+19)(1+\frac{19}{2})(1+\frac{19}{3})...(1+\frac{19}{17})}\)
b) \(B=\frac{1}{-2}.\frac{1}{3}+\frac{1}{-3}.\frac{1}{4}+...+\frac{1}{-5}.\frac{1}{10}\)
c) \(C=(1-\frac{1}{1.2})+(1-\frac{1}{2.3})+...+(1-\frac{1}{2015.2016})\)
d) \(D=\frac{\frac{9}{1}+\frac{8}{2}+\frac{7}{3}+...+\frac{1}{9}}{\frac{1}{2}+\frac{1}{3}+\frac{1}{3}+...+\frac{1}{10}}\)
tính giá trị các biểu thức sau bằng cách hợp lý
a, (\(6^3\)+ 3 x \(6^2\)+ \(3^3\)) : 13
b, \(\frac{8\frac{3}{19}\cdot5\frac{1}{4}+3\frac{16}{19}\cdot5\frac{1}{4}}{\left(2\frac{14}{17}-2\frac{1}{34}\right).34}\)
c, \(\frac{3}{1.6}\)+ \(\frac{3}{6.11}\)+\(\frac{3}{11.16}\)+....+\(\frac{3}{96.101}\)
làm câu nào cg đc cần gấp
1\(\frac{6}{41}\)x (\(\frac{12+\frac{12}{19}-\frac{12}{37}-\frac{12}{53}}{3+\frac{1}{3}-\frac{3}{37}-\frac{3}{53}}\)x\(\frac{4+\frac{4}{17}+\frac{4}{19}+\frac{4}{2006}}{5+\frac{5}{17}+\frac{5}{19}+\frac{5}{2000}}\))x\(\frac{124242423}{237373735}\)
Tính A=\(\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{18}+\frac{1}{19}+\frac{1}{20}}{\frac{19}{1}+\frac{18}{2}+\frac{17}{3}+...+\frac{3}{17}+\frac{2}{18}+\frac{1}{19}}\)
BÀI 1 : Thực hiện phép tính
a) \(\frac{15}{7}\)x \(\frac{4}{3}\)+ \(\frac{6}{3}\)=
b) \(\frac{-13}{41}\)x \(\frac{17}{11}\)x \(\frac{11}{17}\)=
c) \(\frac{-19}{15}\)x \(\frac{5}{8}\)x \(\frac{15}{-19}\)x (-16) =
BÀI 2 : Tính giá trị các biểu thức sau
A = \(\frac{17}{19}\)x \(\frac{-3}{41}\)x \(\frac{19}{17}\)=
B = \(\frac{5}{29}\)x \(\frac{-3}{41}\)x\(\frac{29}{5}\)=
C = \(\frac{-5}{9}\)x \(\frac{23}{28}\)- \(\frac{23}{28}\)x \(\frac{4}{9}\)=
BÀI 3 :Tính giá trị các biểu thức sau một cách hợp lí
M = \(\frac{37}{19}\)x \(\frac{8}{11}\)+ \(\frac{37}{19}\)x \(\frac{3}{11}\)+ \(\frac{12}{19}\)=
N = \(\frac{7}{17}\)x\(\frac{8}{21}\)+ \(\frac{7}{17}\)x\(\frac{13}{21}\)+ \(\frac{10}{17}\)=
