bài 1
a) -2/3 + 5/12 = -1/4
b) -2/9 - 5/12 = -23/36
c) -1 1/4 - 2 1/4 = -7/2
bài 2
a) (1/8 + /3/4) : 5/6 + 1/2
= 7/8 : 5/6 + 1/2
= 21/20 + 1/2
= 31/20
b) 1/2 + 3/4 - (3/4 - 4/5)
= 1/2 + 3/4 - -1/20
= 5/4 - (-1/20)
= 13/10
c) 2/3 + 1/3 x (-4/9 + 5/6)
= 2/3 + 1/3 x 7/18
= 2/3 + (1/3 x 7/18)
= 2/3 +7/54
= 43/54
dạng tìm x
bài 1
-5/6 - x = 2/3
x = -5/6 - 2/3
x = -3/2
1/2x + 3/4 = -3/10
1/2x = -3/10 - 3/4
1/2x = -21/20
x = -21/20 : 1/2
x = -21/10
:v
1,
\(a,\dfrac{-2}{3}+\dfrac{5}{12}=\dfrac{-8}{12}+\dfrac{5}{12}=\dfrac{-3}{12}=-\dfrac{1}{4}\)
\(b,\dfrac{-2}{9}-\dfrac{5}{12}=\dfrac{-8}{36}-\dfrac{15}{36}=-\dfrac{23}{36}\)
\(c,-1\dfrac{1}{4}-2\dfrac{1}{4}=-\dfrac{5}{4}-\dfrac{9}{4}=-\dfrac{14}{4}=-\dfrac{7}{2}\)
2,
\(a,\left(\dfrac{1}{8}+\dfrac{-3}{4}\right):\dfrac{5}{6}+\dfrac{1}{2}\)
\(=-\dfrac{5}{8}:\dfrac{5}{6}+\dfrac{1}{2}=-\dfrac{3}{4}+\dfrac{1}{2}=-\dfrac{3}{4}+\dfrac{2}{4}=-\dfrac{1}{4}\)
\(b,\dfrac{1}{2}+\dfrac{3}{4}-\left(\dfrac{3}{4}-\dfrac{4}{5}\right)\)
\(=\dfrac{5}{4}-\left(-\dfrac{1}{20}\right)=\dfrac{13}{10}\)
\(c,\dfrac{2}{3}+\dfrac{1}{3}\cdot\left(-\dfrac{4}{9}+\dfrac{5}{6}\right)\)
\(=1\cdot\dfrac{7}{18}=\dfrac{7}{18}\)
3,
\(\dfrac{7}{5}\cdot\dfrac{8}{19}+\dfrac{7}{5}\cdot\dfrac{12}{19}-\dfrac{7}{5}\cdot\dfrac{1}{19}\)
\(=\dfrac{7}{5}\cdot\left(\dfrac{8}{19}+\dfrac{12}{19}-\dfrac{1}{19}\right)=\dfrac{7}{5}\)
\(\dfrac{-3}{5}\cdot\dfrac{5}{7}+\dfrac{-3}{5}\cdot\dfrac{3}{7}+\dfrac{-3}{5}\cdot\dfrac{6}{7}\)
\(=\dfrac{-3}{5}\cdot\left(\dfrac{5}{7}+\dfrac{3}{7}+\dfrac{6}{7}\right)=\dfrac{-3}{5}\cdot2=\dfrac{-6}{5}\)
1,
\(\dfrac{-5}{6}-x=\dfrac{2}{3}\)
\(x=\dfrac{-5}{6}-\dfrac{2}{3}\)
\(x=\dfrac{-9}{6}=\dfrac{-3}{2}\)
\(\dfrac{1}{2}x+\dfrac{3}{4}=\dfrac{-3}{10}\)
\(\dfrac{1}{2}x=\dfrac{-3}{10}-\dfrac{3}{4}\)
\(\dfrac{1}{2}x=-\dfrac{21}{20}\)
\(x=-\dfrac{21}{20}:\dfrac{1}{2}\)
\(x=-\dfrac{21}{10}\)
2,
\(a,x=-255\)
\(b,x+30\%=-1,3\)
\(x+\dfrac{3}{10}=-\dfrac{13}{10}\)
\(x=-\dfrac{13}{10}-\dfrac{3}{10}\)
\(x=-\dfrac{16}{10}=-\dfrac{8}{5}\)
\(c,\dfrac{2}{3}+x=45\%\)
\(\dfrac{2}{3}+x=\dfrac{9}{20}\)
\(x=\dfrac{9}{20}-\dfrac{2}{3}\)
\(x=-\dfrac{13}{60}\)
bài 1
a) -2/3 + 5/12 = -1/4
b) -2/9 - 5/12 = -23/36
c) -1 1/4 - 2 1/4 = -7/2
bài 2
a) (1/8 + /3/4) : 5/6 + 1/2
= 7/8 : 5/6 + 1/2
= 21/20 + 1/2
= 31/20
b) 1/2 + 3/4 - (3/4 - 4/5)
= 1/2 + 3/4 - -1/20
= 5/4 - (-1/20)
= 13/10
c) 2/3 + 1/3 x (-4/9 + 5/6)
= 2/3 + 1/3 x 7/18
= 2/3 + (1/3 x 7/18)
= 2/3 +7/54
= 43/54
dạng tìm x
bài 1
-5/6 - x = 2/3
x = -5/6 - 2/3
x = -3/2
1/2x + 3/4 = -3/10
1/2x = -3/10 - 3/4
1/2x = -21/20
x = -21/20 : 1/2
x = -21/10