\(\dfrac{8}{20};\dfrac{35}{20}\)

\(\dfrac{3}{8};\dfrac{14}{8}\)

\(\dfrac{8}{20};\dfrac{35}{20}\\ \dfrac{12}{32};\dfrac{56}{32}\)

\(=\dfrac{5.3.1}{7.4.2}=\dfrac{15}{14.4}=\dfrac{15}{56}\)

\(=\dfrac{3.5.14}{4.7.15}=\dfrac{3.5.7.2}{2.2.7.3.5}=\dfrac{1}{2}\)

a; \(=\dfrac{5\cdot3\cdot1}{7\cdot4\cdot2}=\dfrac{15}{56}\)

b: \(=\dfrac{3\cdot5\cdot14}{4\cdot7\cdot15}=\dfrac{210}{420}=\dfrac{1}{2}\)

a: \(x-\frac25+\frac{7}{12}=\frac12\cdot\frac34\cdot\frac{-9}{16}\)

=>\(x-\frac{24}{60}+\frac{35}{60}=\frac38\cdot\frac{-9}{16}=\frac{-27}{128}\)

=>\(x=-\frac{27}{128}-\frac{11}{60}=\frac{-27\cdot15-11\cdot32}{1920}=-\frac{757}{1920}\)

b: \(\frac49x-\frac12=-\frac59\)

=>\(\frac49x=-\frac59+\frac12=\frac{-10+9}{18}=\frac{-1}{18}\)

=>\(x=-\frac{1}{18}:\frac49=-\frac{1}{18}\cdot\frac94=\frac{-1}{2\cdot4}=-\frac18\)

c: \(-\frac23x+\frac58=\frac{7}{12}\)

=>\(-\frac23x=\frac{7}{12}-\frac58=\frac{14}{24}-\frac{15}{24}=-\frac{1}{24}\)

=>\(x=\frac{1}{24}:\frac23=\frac{1}{24}\cdot\frac32=\frac{1}{8\cdot2}=\frac{1}{16}\)

d: \(\frac25x:\frac73\cdot\frac18=\frac{29}{15}\)

=>\(x\cdot\frac25\cdot\frac37\cdot\frac18=\frac{29}{15}\)

=>\(x\cdot\frac{3}{4\cdot5\cdot7}=\frac{29}{15}\)

=>\(x=\frac{29}{15}:\frac{3}{140}=\frac{29}{15}\cdot\frac{140}{3}=\frac{29\cdot28}{3\cdot3}=\frac{812}{9}\)

a)(x+3)2-x2+15=2x+6-2x+15=1

                        =21=1

Bạn chép sai đầu bài à

x2 là x^2 à

giúp 

_P^LEA^SE

c

\(67-\left[8+7.3^2-24:6+\left(9-7\right)^3\right]:15\\ =67-\left[8+7.9-4+2^3\right]:15\\ =67-\left[8+63-4+8\right]:15\\ =67-75:15\\ =67-5=62\)

cảm ơn bạn Nguyễn Hòang tùng nhé

\(a,\dfrac{1}{2}-\dfrac{1}{3}-\left(-\dfrac{5}{4}\right)=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{5}{4}=\dfrac{1\times6-1\times4+5\times3}{12}=\dfrac{6-4+15}{12}=\dfrac{17}{12}\\ b,\dfrac{5}{4}-\dfrac{1}{2}-\dfrac{7}{8}=\dfrac{5\times2-1\times4-7}{8}=\dfrac{10-4-7}{8}=-\dfrac{1}{8}\\ c,\dfrac{1}{5}-\dfrac{1}{2}+\dfrac{9}{10}=\dfrac{1\times2-1\times5+9}{10}=\dfrac{2-5+9}{10}=\dfrac{6}{10}=\dfrac{3}{5}\\ d,\dfrac{5}{4}-\dfrac{1}{3}+\dfrac{7}{6}=\dfrac{5\times3-1\times4+7\times2}{12}=\dfrac{15-4+14}{12}=\dfrac{25}{12}\)

`1/2+(-1/3)-(-5/4)`

`=1/2-1/3+5/4`

`=3/6-2/6+5/4`

`=1/6+5/4`

`=2/12+15/12`

`=17/12`

__

`5/4-1/2+(-7/8)`

`=5/4-1/2-7/8`

`=10/8-4/8-7/8`

`=6/8-7/8`

`=-1/8`

__

`1/5-1/2+9/10`

`=2/10-5/10+9/10`

`=-3/10+9/10`

`=6/10`

`=3/5`

__

`5/4-1/3+7/6`

`=15/12-4/12+14/12`

`=11/12+14/12`

`=25/12`

`#lv`

a) \(\frac{2^3.3^4}{2^2.3^2.5}=\frac{2.3^2}{1.1.5}=\frac{18}{5}\)

b) \(\frac{2^4.5^2.11^2.7}{2^3.5^3.7^2.11}=\frac{2.1.11.1}{1.5.7.1}=\frac{22}{35}\)