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(x-1/2)*5/3=7/4-1/2
(x-1/2)*5/3=5/4
x-1/2=3/4
x = 5/4
(x+4/3)*7/4=5-7/6
(x+4/3)*7/4=23/6
x+4/3 = 46/21
x = 6/7
6/8=15/x
6*x=15*8
6*x=120
x = 20
\(\frac{6}{8}=\frac{15}{x}\)
\(\Rightarrow x=\left(15\cdot8\right):6\)
\(\Rightarrow x=20\)
1/4 + 2/5 + 6/8 + 9/15 + 6/7 = ( 1/4 + 6/8 ) + ( 2/5 + 9/15 ) + 6/7
= 1 + 1 + 6/7
= 2 + 6/7
= 20/7
\(\frac{1}{4}+\frac{2}{5}+\frac{6}{8}+\frac{9}{15}+\frac{6}{7}\)
= \(\left(\frac{1}{4}+\frac{6}{8}\right)+\left(\frac{2}{5}+\frac{9}{15}\right)+\frac{6}{7}\)
= \(1+1+\frac{6}{7}\)
= 2 + \(\frac{6}{7}\)
= \(\frac{14}{7}+\frac{6}{7}=\frac{20}{7}\)
a) \(\frac{11}{15}+\frac{5}{7}+\frac{2}{7}+\frac{4}{15}=\left(\frac{11}{15}+\frac{4}{15}\right)+\left(\frac{5}{7}+\frac{2}{7}\right)\)
\(=2\)
b) \(\frac{5}{9}\times\frac{1}{2}\times\frac{5}{9}\times\frac{6}{4}=\frac{25}{81}\times\frac{3}{4}=\frac{25}{108}\)
c) \(\frac{7}{8}\div\frac{1}{2}+\frac{9}{8}\div\frac{1}{2}=\left(\frac{7}{8}+\frac{9}{8}\right)\div\frac{1}{2}\)
\(=2\div\frac{1}{2}=4\)
d) \(\frac{17}{10}+\frac{1}{2}-\frac{7}{10}=\left(\frac{17}{10}-\frac{7}{10}\right)+\frac{1}{2}\)
\(=1+\frac{1}{2}=\frac{3}{2}\)
a) \(\frac{11}{15}+\frac{5}{7}+\frac{2}{7}+\frac{4}{15}\)
\(=\left(\frac{11}{15}+\frac{4}{15}\right)+\left(\frac{5}{7}+\frac{2}{7}\right)\)
\(=1+1\)
\(=2\)
b) \(\frac{5}{9}.\frac{1}{2}.\frac{5}{9}.\frac{6}{4}\)
\(=\left(\frac{5}{9}\right)^2\left(\frac{1}{2}.\frac{6}{4}\right)\)
\(=\frac{25}{81}.\frac{3}{4}\)
\(=\frac{25}{108}\)
c) \(\frac{7}{8}:\frac{1}{2}+\frac{9}{8}:\frac{1}{2}\)
\(=\frac{7}{8}.2+\frac{9}{8}.2\)
\(=2\left(\frac{7}{8}+\frac{9}{8}\right)\)
\(=2.\frac{16}{8}\)
\(=2.2\)
\(=4\)
d) \(\frac{17}{10}+\frac{1}{2}-\frac{7}{10}\)
\(=\left(\frac{17}{10}-\frac{7}{10}\right)+\frac{1}{2}\)
\(=1+\frac{1}{2}\)
\(=\frac{2}{2}+\frac{1}{2}\)
\(=\frac{3}{2}\)
a, 6/9+5/7+1/3=2/3+5/7+1/3=5/7+1=12/7
b, 17/7+6/5-20/14=17/7+6/5-10/7=6/5+1=11/5
c,2/5x1/4+3/4x2/5=2/5x(1/4+3/4)=2/5x1=2/5
d, 6/11:4/6+5/11:2/3=6/11:2/3+5/11:2/3=(6/11+5/11):2/3=3/2
nha
bài 6 \(\frac{2}{2\times4}+\frac{2}{4\times6}+\frac{2}{6\times8}+\ldots+\frac{2}{80\times82}+\frac{2}{82\times84}\)
= \(\frac12-\frac14+\frac14-\frac16+\frac16-\cdots+\frac{1}{80}-\frac{1}{82}+\frac{1}{82}-\frac{1}{84}\)
= \(\frac12-\left(\frac14-\frac14\right)-\left(\frac16-\frac16\right)-\cdots-\left(\frac{1}{82}-\frac{1}{82}\right)-\frac{1}{84}\)
=\(\frac12-0-0-\frac{1}{84}\)
=\(\frac12\) - \(\frac{1}{84}\)
=\(\frac{42}{84}-\frac{1}{84}\)
=\(\frac{41}{84}\)
Bài 7
a)\(\frac{19}{4}=4\frac34\)
b)\(\frac{27}{5}=5\frac25\)
c)\(\frac{56}{8}=7\frac08\)
a,(11/15+4/15)+(5/7+2/7)
=1+1
=2
b,5/9x(1/2+6/4)
=5/9x2
=10/9
c,1/2:(7/8+9/8)
=1/2:2
=1
d,(17/10-7/10)+1/2
=1+1/2
=3/2
\(\frac{3}{4}\)x \(\frac{15}{7}\)+ \(\frac{6}{7}\)x \(\frac{6}{8}\)
= \(\frac{45}{28}\)+ \(\frac{9}{14}\)
= \(\frac{9}{4}\)
#Hoctot
\(\frac{3}{4}\times\frac{15}{7}+\frac{6}{7}\times\frac{6}{8}\)
\(=\frac{3}{4}\times\frac{15}{7}+\frac{6}{7}\times\frac{3}{4}\)
\(=\frac{3}{4}\times\left(\frac{15}{7}+\frac{6}{7}\right)\)
\(=\frac{3}{4}\times3\)
\(=\frac{9}{4}\)
Học tốt
3/4×15/7+6/7×6/8
45/28+9/14
9/4
\(\frac{3}{4}\)x \(\frac{15}{7}+\frac{6}{7}x\frac{6}{8}\)
= \(\frac{3}{4}x\frac{15}{7}+\frac{6}{7}x\frac{3}{4}\)
= \(\frac{3}{4}x\)(\(\frac{15}{7}+\frac{6}{7}\))
= \(\frac{3}{4}x3=\frac{9}{4}\)
\(\frac{3}{4}\)x \(\frac{15}{7}\)+ \(\frac{6}{7}\)x \(\frac{6}{8}\)= \(\frac{3}{4}\) x \(\frac{15}{7}\)+ \(\frac{6}{7}\)x \(\frac{3}{4}\)=
3 / 4 x ( 15/7 + 6/7 ) = 3/4 x 3/1 = 9/4
Học tốt ^^ ( Xin lỗi bạn , máy mik bị lag nên lúc đầu viết đc phân số , lúc sau lại không nên đành phải thế , xin lỗi vì sự sai sót này )
\(\frac{3}{4}\cdot\frac{15}{7}+\frac{6}{7}\cdot\frac{6}{8}\)
\(=\frac{45}{28}+\frac{2.3+2.3}{7.2.2.2}=\frac{45}{28}+\frac{9}{14}=\frac{9}{4}\)