nhớ giải bằng cách hợp lí ra nhé

a, -10

b, 20

c, -20

d, -30

a) 10 – 12 – 8 = 10 – (12 + 8) = 10  - 20 = - 10

b) 4 – (- 15) – 5 + 6 = (4 + 6) – [(-15) + 5)] = 10 – (- 10) = 10 + 10 = 20

c) 2 – 12 – 4 – 6 = (2 – 12) - (4 + 6) = -10 + (- 10) = - 20

d) – 45 – 5 – (- 12) + 8 = - (45 + 5) + (12 + 8) = (- 50) + 20 = - 30

a) 10-12-8=2-12=-10

b) 4-(-15)-5+6=4+15-5+6=10+10=20

c) 2-12-4-6=-10-10=-20

d) -45-5-(-12)+8=-50+12+8=-50+20=-30

a)\(\left( { - 0,4} \right) + \frac{3}{8} + \left( { - 0,6} \right) = \left[ {\left( { - 0,4} \right) + \left( { - 0,6} \right)} \right] + \frac{3}{8} =  - 1 + \frac{3}{8} = \frac{{ - 5}}{8}\).

b)

\(\frac{4}{5} - 1,8 + 0,375 + \frac{5}{8} = (0,8 - 1,8) + (0,375 + 0,625) = ( - 1) + 1 = 0\)

\(=\left(-\dfrac{3}{11}-\dfrac{8}{11}\right)+\left(\dfrac{11}{8}-\dfrac{3}{8}\right)=0\)

\(\frac{18}{23}:9\)

\(=\frac{18}{23}\times\frac{1}{9}\)

\(=\frac{2}{23}\times\frac{1}{1}\)

\(=\frac{2}{23}\)

\(8:\frac{3}{4}:\frac{4}{9}\)

\(=\frac{8}{1}\times\frac{4}{3}\times\frac{4}{9}\)

\(=\frac{32}{3}\times\frac{4}{9}\)

\(=\frac{128}{27}\)

bài 1:

\(\frac{18}{23}:9\)=\(\frac{18}{207}\)=\(\frac{2}{23}\)

\(8:\frac{3}{4}:\frac{4}{9}\)=\(\frac{8}{1}.\frac{4}{3}.\frac{9}{4}\)=24

bài 2:

0,25 x 6,9 x 4=(0,25 x 4) x 6,9

=6,9

mấy câu sau làm tương tự

Bài 1 :

\(\frac{18}{23}:9=\frac{2}{23}\)                \(8:\frac{3}{4}:\frac{4}{9}=\frac{32}{3}:\frac{4}{9}=24\)

Bài 2 :

0,25 x 6,9 x 4

= 0,25 x 4 x 6,9

= 1 x 6,9

= 6,9

7,2 x 4,7 + 72 : 0,1 + 7,2 x 4,3 

= 7,2 x 4,7 + 7,2 x 10 + 7,2 x 4,3

= 7,2 x ( 4,7 + 10 + 4,3 )

= 7,2 x 19

= 136,8

14,7 x 31 + 29,4 + 67 x 14,7

= 14,7 x 31 + 14,7 x 2 + 67 x 14,7

= 14,7 x ( 31 + 2 + 67 )

= 14,7 x 100

= 1470

20,19 x 6 + 20,19 + 3 x 20,19

= 20,19 x ( 6 + 1 + 3 )

= 20,19 x 10

= 201,9

~ Thiên Mã ~

\(\frac{18}{23}.\frac{1}{9}=\frac{2}{23}.\frac{1}{1}=\frac{2}{23}\\ 8.\frac{4}{3}.\frac{9}{4}=8.\frac{1}{3}.\frac{9}{1}=\frac{8}{3}.9=\frac{72}{3}=4\\ mìnhchỉghicáchlàmkhôngghiđềbàinha\)

1:

a: \(=\dfrac{-4}{7}+\dfrac{4}{7}+\dfrac{3}{7}-\dfrac{23}{34}-\dfrac{4}{5}=\dfrac{3}{7}-\dfrac{23}{34}-\dfrac{4}{5}=-\dfrac{1247}{1190}\)

b:

Sửa đề: \(\dfrac{-5}{13}+\dfrac{4}{19}+\dfrac{-8}{13}+\dfrac{15}{19}+\dfrac{45}{6}\) 

\(=\dfrac{-5}{13}-\dfrac{8}{13}+\dfrac{4}{19}+\dfrac{15}{19}+\dfrac{45}{6}=\dfrac{9}{2}\)

a) (-1) + 2 + (-3) + 4 + .... + (-2009) + 2010

= (-1 + 2) + (-3 + 4) + ..... + (-2009 + 2010)

= -1 + (-1) + (-1) + .... + (-1) 

= -1 . 1005 = -1005

b) 1 + (-2) + (-3) + 4 + 5 + (-6) + (-7) + 8 + ... + 2005 + (-2006) + (-2007) + 2008

= [1 + (-2) + (-3) + 4] + [5 + (-6) + (-7) + 8 ] + ..... + [2005 + (-2006) + (-2007) + 2008]

= 0 + 0 + ...... + 0 = 0

ghe

a) Ta có: \(\left(-1\right)+2+\left(-3\right)+4+...+\left(-2009\right)+2010\)

\(=1+1+...+1\)

=1005

b) Ta có: \(1+\left(-2\right)+\left(-3\right)+4+5+\left(-6\right)+\left(-7\right)+8+...+2005+\left(-2006\right)+\left(-2007\right)+2008\)

\(=\left(1-2-3+4\right)+\left(5-6-7+8\right)+...+\left(2005-2006-2007+2008\right)\)

=0

a: \(=\dfrac{3}{7}+\dfrac{7}{8}+\dfrac{4}{7}-\dfrac{15}{8}=1-1=0\)

b: \(=\dfrac{1}{2}+\dfrac{4}{5}+\dfrac{3}{8}-\dfrac{7}{40}+\dfrac{1}{2}\)

\(=1+\dfrac{32+15-7}{40}=1+1=2\)