bài 1:a) 65/91+-33/55
b)36/-84+100/450
c)(-2/5+1/3).(3/2-3/7)
d)(1/2-1/3).(5-1/4)
e)2/3-4.(1/2+3/4)
MN ơi GIÚP EM VỚI Ạ
K
Khách
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16 tháng 11 2021
1/ 1 + (-2) + 3 + (-4) + . . . + 19 + (-20)
=1-2+3-4+...+19-20
=(1-2)+(3-4)+...+(19-20)
=(-1)+(-1)+...+(-1)
=(-1).10
=-10
2/ 1 – 2 + 3 – 4 + . . . + 99 – 100
=(1-2)+(3-4)+...+(99-100)
=(-1)+(-1)+...+(-1)
=(-1).50
=-50
3/ 2 – 4 + 6 – 8 + . . . + 48 – 50
=(2-4)+(6-8)+...+(48-50)
=(-2)+(-2)+...+(-2)
=(-2).13
=-26
4/ – 1 + 3 – 5 + 7 - . . . . + 97 – 99
=(-1)+(3-5)+(7-9)+...+(97-99)
=(-1)+(-2)+(-2)+...+(-2)
=(-1)+(-2).45
=(-1)+(-90)
=(-91)
5/ 1 + 2 – 3 – 4 + . . . . + 97 + 98 – 99 - 100
=(1+2-3-4)+...+(97 + 98 – 99 - 100)
=(-4)+...+(-4)
=(-4).25
=-100
\(HT\)
YN
16 tháng 11 2021
1/ \(1+(-2)+3+(-4)+...+19+(-20)\)
\(=(-1+3+5+...+19)-(2+4+6+...+20)\)
\(=(19-1):2+1=10\)
\(=(1+19).10:2-(20+2).10:2\)
\(=100-110\)
\(=-10\)
2/ \(1 – 2 + 3 – 4 + . . . + 99 – 100\)
\(= ( 1 - 2 ) + ( 3 - 4) + .... + ( 99 - 100 )\)
\(= -1 + ( -1) + ....+ ( -1)\)
\(=(-1).50\)
\(=-50\)
3/ 
\( 2 – 4 + 6 – 8 + . . . + 48 – 50\)
\(= 2 +( – 4 + 6)+( – 8+10) + . . . +( -44+46)+ ( 48 – 50)\)
\(= 2+2+2+...+2+( -2) \)
\(= 2.12 +( -2 ) \)
\(=22\)
4/ \(-1+3-5+7-...+97-99\)
\(= ( -1 + 3 ) + ( -5 + 7 )+....+( -93 +95 ) + ( 97 - 99 )\)
\(= -2+( -2)+...+( -2)+2\)
\(= -2.24+2\)
\(=-46\)
5/ \( 1+2-3-4+...+97+98-99-100\)
\(= ( 1+2-3-4)+...+( 97+98-99-100)\)
\(= -4+...+( -4)\)
\(=(-4).25\)
\(=-100\)
20 tháng 3 2022
A) 3/4 + 1/5 = 15/20 + 4/20= 19/20
B) 1/36 + 5/12 = 12/432 + 180/432=192/864
C) 3/4 + 1/6 = 18/24 + 4/24 = 22/24
D) 1/8 + 7/10 = 10/80 + 56/80=66/160
E) 1/8 + 5/6= 6/48 + 40/48= 46/48
G) 2/3 + 2/7 = 14/21+6/24= 20/24
K nha
20 tháng 3 2022
A\(\frac{1}{4}+\frac{2}{3}=\frac{3}{12}+\frac{8}{12}=\frac{11}{12}\)
B\(\frac{2}{7}+\frac{2}{3}=\frac{6}{21}+\frac{14}{21}=\frac{20}{21}\)
C\(\frac{2}{5}+\frac{1}{4}=\frac{8}{20}+\frac{5}{20}=\frac{13}{20}\)
D\(\frac{1}{2}+\frac{1}{3}=\frac{3}{6}+\frac{2}{6}=\frac{5}{6}\)
E\(\frac{1}{3}+\frac{3}{5}=\frac{5}{15}+\frac{9}{15}=\frac{14}{15}\)
G\(\frac{4}{5}+\frac{1}{2}=\frac{8}{10}+\frac{5}{10}=\frac{13}{10}\)
20 tháng 3 2022
a, 1/4 + 2/3 = 2/12 + 8/12 = 10/12 = 5/6
b, 2/7 +2/3 = 6/21 + 14/21 = 20/21
c, 2/5 + 1/4 = 8/20 + 5/20 = 13/20
d, 1/2 + 1/3 = 3/6 + 2/6 = 5/6
e, 1/3 + 3/5 = 5/15 + 9/15 =14/15
g, 4/5 + 1/2 = 8/10 + 5/10 = 13/10
17 tháng 10 2021
1: Ta có: \(20-2\left(x+4\right)=4\)
\(\Leftrightarrow2\left(x+4\right)=16\)
\(\Leftrightarrow x+4=8\)
hay x=4
5: Ta có: \(\left(x+1\right)^3=27\)
\(\Leftrightarrow x+1=3\)
hay x=2
25 tháng 4 2020
https://www.youtube.com/channel/UC5odkiOvzz9Rvu3HUYlL2IQ?view_as=subscriber
NX
16 tháng 8 2023
a) \(\dfrac{13}{20}+\dfrac{3}{5}+x=\dfrac{5}{6}\)
\(\Rightarrow\dfrac{5}{4}+x=\dfrac{5}{6}\)
\(\Rightarrow x=\dfrac{5}{6}-\dfrac{5}{4}\)
\(\Rightarrow x=\dfrac{-5}{12}\)
b) \(x+\dfrac{1}{3}=\dfrac{2}{5}-\dfrac{-1}{3}\)
\(\Rightarrow x+\dfrac{1}{3}=\dfrac{11}{15}\)
\(\Rightarrow x=\dfrac{11}{15}-\dfrac{1}{3}\)
\(\Rightarrow x=\dfrac{2}{5}\)
c)\(\dfrac{-5}{8}-x=\dfrac{-3}{20}-\dfrac{-1}{6}\)
\(\dfrac{-5}{8}-x=\dfrac{1}{60}\)
\(\Rightarrow x=\dfrac{-5}{8}-\dfrac{1}{60}\)
\(\Rightarrow x=\dfrac{-77}{120}\)
d) \(\dfrac{3}{5}-x=\dfrac{1}{4}+\dfrac{7}{10}\)
\(\Rightarrow\dfrac{3}{5}-x=\dfrac{19}{20}\)
\(\Rightarrow x=\dfrac{3}{5}-\dfrac{19}{20}\)
\(\Rightarrow x=\dfrac{-7}{20}\)
e) \(\dfrac{-3}{7}-x=\dfrac{4}{5}+\dfrac{-2}{3}\)
\(\Rightarrow\dfrac{-3}{7}-x=\dfrac{2}{15}\)
\(\Rightarrow x=\dfrac{-3}{7}-\dfrac{2}{15}\)
\(\Rightarrow x=\dfrac{-59}{105}\)
NX
16 tháng 8 2023
g) \(\dfrac{-5}{6}-x=\dfrac{7}{12}+\dfrac{-1}{3}\)
\(\Rightarrow\dfrac{-5}{6}-x=\dfrac{1}{4}\)
\(\Rightarrow x=\dfrac{-5}{6}-\dfrac{1}{4}\)
\(\Rightarrow x=\dfrac{-13}{12}\)
Bài 1:
a) \(\dfrac{65}{91}+\dfrac{-33}{55}=\dfrac{5}{7}+\dfrac{-3}{5}=\dfrac{25}{35}+\dfrac{-21}{35}=\dfrac{4}{35}\)
b) \(\dfrac{36}{-84}+\dfrac{100}{450}=\dfrac{-3}{7}+\dfrac{2}{9}=\dfrac{-27}{63}+\dfrac{14}{63}=\dfrac{-13}{63}\)