Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
a) \(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}\)
\(=1-\frac{1}{4}\)
\(=\frac{3}{4}\)
b) \(\frac{4}{7}\times\frac{8}{9}+\frac{4}{7}\times\frac{1}{9}\)
\(=\frac{4}{7}\times\left(\frac{8}{9}+\frac{1}{9}\right)\)
\(=\frac{4}{7}\times1\)
\(=\frac{4}{7}\)
c) \(\frac{13}{6}\times\frac{3}{8}-\frac{3}{8}\times\frac{7}{6}\)
\(=\frac{3}{8}\times\left(\frac{13}{6}-\frac{7}{6}\right)\)
\(=\frac{3}{8}\times1\)
\(=\frac{3}{8}\)
d) \(\frac{1}{1x2}+\frac{1}{2x3}+\frac{1}{3x4}+...+\frac{1}{9x10}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}\)
\(=1-\frac{1}{10}\)
\(=\frac{9}{10}\)
1 ] 2/3 : 1/2 + 1/3 : 1/2
= 2/3 x 2/1 + 1/3 x 2/1
= 2/1 x ( 2/3 + 1/3 )
= 2 x 1
= 2
2 ] 3/10 : 7/6 : 3/7
= 3/10 x 6/7 x 7/3
= 3 x 6 x 7 / 10 x 7 x 3
= [ tách 6 và 10 ] 3 x 3 x 2 x 7 / 2 x 5 x 7 x 3
= [ Gạch chéo các số trùng nhau trong tử số và mẫu số , đó là rút gọn ]
= 3 / 5
3 ] 4/5 x 7/9 : 7/5
= 4/5 x 7/9 x 5/7
[ làm như phép tính 2 ]
4 ] ( 1 - 1/2 ) x ( 1 - 1/3 ) x ( 1 - 1/4 ) x ( 1 - 1/5 )
= 1/2 x 2/3 x 3/4 x 4/5
= 1 x 2 x 3 x 4 / 2 x 3 x 4 x 5
= [ gạch các số trùng nhau trong tử số và mẫu số ]
= 1/5
2/3:1/2+1/3:1/2
bằng3/2 nhân 1/2 + 3/1 nhân 1/2
bằng3/4+3/2 bằng 3/4 + 6/4 bằng 9/4
\(\frac{2}{5}+1=\frac{2+5}{5}=\frac{7}{5}\)
\(\frac{6}{7}.4=\frac{6.4}{7}=\frac{24}{7}\)
\(\frac{3}{7}:2=\frac{3}{7.2}=\frac{3}{14}\)
\(2:\frac{2}{4}=\frac{2.4}{2}=4\)
\(\frac{3}{4}.\frac{2}{9}+\frac{1}{3}=\frac{6}{36}+\frac{1}{3}=\frac{1}{6}+\frac{1}{3}=\frac{1}{2}\)
\(\frac{1}{4}:\frac{1}{3}-\frac{1}{2}=\frac{3}{4}-\frac{1}{2}=\frac{1}{4}\)
2/5 + 1 = 7/5
6/7 x 4 =24 /7
3/7 :2 =1/7
2:2/4 = 4
3/4 x 2/9 + 1/3 = 1/2
1/4 : 1/3 - 1/2 = 1/4
4/7x9/5-3/7+4/7:5/6+6/7x2
=36/35-3/7+24/35+12/7
=36/35-15/35+24/35+60/35
=21/35+24/35+60/35
=45/35+60/35
=105/35
=3
\(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\)
= \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}\)
= \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\)
= \(1-\frac{1}{7}\)
= \(\frac{7}{7}-\frac{1}{7}\)
= \(\frac{6}{7}\)
2) \(\frac{7}{4}-x.\frac{4}{3}=\frac{5}{19}\)
\(x.\frac{4}{3}=\frac{7}{4}-\frac{5}{19}\)
\(x.\frac{4}{3}=\frac{133}{76}-\frac{20}{76}\)
\(x.\frac{4}{3}=\frac{113}{76}\)
\(x=\frac{113}{76}:\frac{4}{3}\)
\(x=\frac{399}{304}\)
VẬY \(x=\frac{399}{304}\)
b) \(\left(x+\frac{3}{4}\right).\frac{5}{7}=\frac{10}{9}\)
\(\left(x+\frac{3}{4}\right)=\frac{10}{9}:\frac{5}{7}\)
\(x+\frac{3}{4}=\frac{14}{9}\)
\(x=\frac{14}{9}-\frac{3}{4}\)
\(x=\frac{29}{36}\)
Vậy \(x=\frac{29}{36}\)
c) \(x.\frac{1}{2}+\frac{3}{2}.x=\frac{4}{5}\)
\(x.\left(\frac{1}{2}+\frac{3}{2}\right)=\frac{4}{5}\)
\(x.2=\frac{4}{5}\)
\(x=\frac{4}{5}:2\)
\(x=\frac{2}{5}\)
Vậy \(x=\frac{2}{5}\)
Chúc bạn học tốt !!!
( 45 - 5 x 9 ) x 1 x 2 x 3 x 4 x 5 x 6 x 7
= ( 45 - 45 ) x 1 x 2 x 3 x 4 x 5 x 6 x 7
= 0 x 1 x 2 x 3 x 4 x 5 x 6 x 7
= 0
( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 ) x ( 72 - 8 x 8 - 8 )
= ( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 ) x ( 72 - 64 - 8 )
= ( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 ) x 0
= 0
a) \(\dfrac{3}{7}\)
b)\(\dfrac{9}{4}\)
c)\(\dfrac{1}{3}\)
d)\(\dfrac{41}{32}\)
e)\(\dfrac{73}{60}\)
a)\(\dfrac{1}{7}+\dfrac{3}{4}\cdot\dfrac{2}{7}=\dfrac{1}{7}+\dfrac{3}{14}=\dfrac{2}{14}+\dfrac{3}{14}=\dfrac{5}{14}\)
b)\(\dfrac{2}{5}:\dfrac{2}{9}\cdot\dfrac{1}{6}=\dfrac{2}{5}\cdot\dfrac{9}{2}\cdot\dfrac{1}{6}=\dfrac{18}{60}\)
c)\(\dfrac{8}{7}-\dfrac{1}{4}\cdot\dfrac{2}{3}=\dfrac{8}{7}-\dfrac{1}{6}=\dfrac{48}{42}-\dfrac{7}{42}=\dfrac{41}{42}\)
d)\(\dfrac{4}{9}\cdot\dfrac{7}{3}+\dfrac{1}{9}=\dfrac{28}{27}+\dfrac{1}{9}=\dfrac{28}{27}+\dfrac{3}{27}=\dfrac{31}{27}\)
. đổi thành x nha
\(a.\dfrac{1}{7}+\dfrac{3}{4}\times\dfrac{2}{7}\\ =\dfrac{1}{7}+\dfrac{3\times2}{4\times7}\\ =\dfrac{1}{7}+\dfrac{6}{28}\\ =\dfrac{1\times4}{7\times4}+\dfrac{6}{28}\\ =\dfrac{4}{28}+\dfrac{6}{28}\\ =\dfrac{4+6}{28}\\ =\dfrac{10}{28}\\ =\dfrac{5}{14}\\ b.\dfrac{2}{5}:\dfrac{2}{9}\times\dfrac{1}{6}\\ =\dfrac{2}{5}\times\dfrac{9}{2}\times\dfrac{1}{6}\\ =\dfrac{2\times9\times1}{5\times2\times6}\\ =\dfrac{18}{60}\\ =\dfrac{3}{10}\\ c.\dfrac{8}{7}-\dfrac{1}{4}\times\dfrac{2}{3}\\ =\dfrac{8}{7}-\dfrac{1\times2}{4\times3}\\ =\dfrac{8}{7}-\dfrac{2}{12}\\ =\dfrac{8\times12}{7\times12}-\dfrac{2\times7}{12\times7}\\ =\dfrac{96}{84}-\dfrac{14}{84}\\ =\dfrac{82}{84}\\ =\dfrac{41}{42}\)
\(\dfrac{4}{9}\times\dfrac{7}{3}+\dfrac{1}{9}\\ =\dfrac{4\times7}{9\times3}+\dfrac{1}{9}\\ =\dfrac{28}{27}+\dfrac{1}{9}\\ =\dfrac{28}{27}+\dfrac{1\times3}{9\times3}\\ =\dfrac{28}{27}+\dfrac{3}{27}\\ =\dfrac{28+3}{27}\\ =\dfrac{31}{27}.\)