1+2+3+5+7+9+10+11=
Bài 1:
a) 8/7 - 5/11 : 8 b) 1 + 2/9 : 7/3 - 10/7 c) 11/3 - 2 : 7/3 + 4
Bài 2:
a) 9/4 - x = 5/11 : 1/2 b) 2/9 : x = 7/3 - 10/7
Bài 3:
\(\dfrac{1999x1998-1}{1997x1999+1998}\)
1:
a: =8/7-5/88=669/616
b: \(=1+\dfrac{2}{9}\cdot\dfrac{3}{7}-\dfrac{10}{7}=1+\dfrac{2}{21}-\dfrac{10}{7}\)
\(=\dfrac{21+2-30}{21}=\dfrac{-7}{21}=\dfrac{-1}{3}\)
c: \(=\dfrac{11}{3}-\dfrac{6}{7}+4=\dfrac{77-18+84}{21}=\dfrac{143}{21}\)
Bài 2:
a: =>9/4-x=5/11*2=10/11
=>x=9/4-10/11=59/44
b: =>2/9:x=19/21
=>x=2/9:19/21=14/57
Tính 1) 4/5 +13/18 2) 3/7 -11/8 3) -7/10 - -4/5 4) 3/20 -1/25 5) 2/3 - 5/6 6) 1/4 + -3/8 - 19/10 7) -9/10 - -7/18 8) 3/10 - 11/18 9) 3/5 -5/6 + -7/12 10) -4/9 - (-5 )/6 - 3/8
1: =72/90+65/90=137/90
2: =24/56-77/56=-53/56
3: =-7/10+4/5=1/10
4: =15/100-4/100=11/100
5: =4/6-5/6=-1/6
6: =10/40-15/40-76/40=-81/40
7: =-9/10+7/18
=-81/90+35/90=-46/90=-23/45
8: =27/90-55/90=-28/90=-14/45
9: =36/60-50/60-35/60=-49/60
10: =-4/9+5/6-3/8
=-32/72+60/72-27/72
=1/72
\(1,\dfrac{4}{5}+\dfrac{13}{18}=\dfrac{72}{90}+\dfrac{65}{90}=\dfrac{137}{90}\)
\(2,\dfrac{3}{7}-\dfrac{11}{8}=\dfrac{24}{56}-\dfrac{77}{56}=\dfrac{-53}{56}\)
\(3,-\dfrac{7}{10}-\left(-\dfrac{4}{5}\right)=-\dfrac{7}{10}-\left(-\dfrac{8}{10}\right)=\dfrac{1}{10}\)
\(4,\dfrac{3}{20}-\dfrac{1}{25}=\dfrac{75}{500}-\dfrac{20}{500}=\dfrac{55}{500}=\dfrac{11}{100}\)
\(5,\dfrac{2}{3}-\dfrac{5}{6}=\dfrac{12}{18}-\dfrac{15}{18}=-\dfrac{3}{18}=-\dfrac{1}{6}\)
\(6,\dfrac{1}{4}+\left(-\dfrac{3}{8}\right)-\dfrac{19}{10}=\dfrac{8}{32}+\left(-\dfrac{12}{32}\right)-\dfrac{19}{10}=-\dfrac{4}{32}-\dfrac{19}{10}\)
\(=-\dfrac{1}{8}-\dfrac{19}{10}=-\dfrac{10}{80}-\dfrac{152}{80}=-\dfrac{162}{80}=-\dfrac{81}{40}\)
\(7,-\dfrac{9}{10}-\left(-\dfrac{7}{18}\right)=-\dfrac{162}{180}-\left(-\dfrac{70}{180}\right)=-\dfrac{92}{180}=-\dfrac{23}{45}\)
\(8,\dfrac{3}{10}-\dfrac{11}{18}=\dfrac{54}{180}-\dfrac{110}{180}=-\dfrac{56}{180}=-\dfrac{14}{45}\)
\(9,\dfrac{3}{5}-\dfrac{5}{6}+\left(-\dfrac{7}{12}\right)=\dfrac{18}{30}-\dfrac{25}{30}+\left(-\dfrac{7}{12}\right)=-\dfrac{7}{30}+\left(-\dfrac{7}{12}\right)\)
\(=-\dfrac{84}{360}+\left(-\dfrac{210}{360}\right)=-\dfrac{294}{360}=-\dfrac{49}{60}\)
\(10,-\dfrac{4}{9}-\dfrac{-5}{6}-\dfrac{3}{8}=-\dfrac{24}{54}-\dfrac{-45}{54}-\dfrac{3}{8}\)
\(=\dfrac{21}{54}-\dfrac{3}{8}=\dfrac{7}{18}-\dfrac{3}{8}=\dfrac{56}{144}-\dfrac{54}{144}=\dfrac{2}{144}=\dfrac{1}{72}\)
`@mt`
Bài 3: Tính
1 + 5 =
2 + 3 =
3 + 6 =
4 + 5 =
5 + 1 =
6 + 2 =
7 + 1 =
8 + 1 =
9 + 0 =
10 + 2=
11 + 2 =
1 + 3 =
2 + 6 =
3 + 7 =
4 + 2 =
5 + 2 =
6 + 3 =
7 + 3 =
8 + 2 =
9 + 1 =
10 + 0 =
11 + 3 =
1 + 4 =
2 + 8 =
3 + 2 =
4 + 1 =
5 + 4 =
6 + 4 =
7 + 2 =
8 + 0 =
9 + 2 =
10 + 6 =
11 + 6 =
Bài 4: Tính
6 - 2 =
3 - 1 =
4 - 2 =
5 - 2 =
8 - 5 =
10 - 6 =
4 - 3 =
3 - 3 =
5 - 1 =
2 - 2 =
3 - 1 =
4 - 1 =
2 - 1 =
4 - 3 =
5 - 0 =
9 - 4 =
8 - 6 =
7 - 3 =
8 - 4 =
7 - 6 =
9 - 5 =
7 - 7=
5 - 3 =
5 - 3=
6 - 3 =
7 - 3 =
7 - 6 =
6 - 5 =
9 - 7 =
9 - 3 =
8 - 8 =
8 - 0 =
5 - 3 =
Bài 5: Tính
6 - 2 =
5 + 2 =
9 - 5 =
2 + 0 =
8 + 2 =
4 - 4 =
7 - 3 =
3 + 6 =
7 + 2 =
9 - 5 =
3 + 6 =
1 + 5 =
7 - 6 =
7 + 1 =
3 + 5 =
2 - 1 =
6 + 3 =
5 + 2 =
9 - 4 =
6 + 4 =
4 + 2 =
6 + 1=
7 - 7=
4 + 3 =
7 + 3 =
5 - 2 =
6 - 5 =
8 - 6 =
6 - 4 =
7 - 3 =
10 + 0 =
5 +4 =
8 - 2 =
a,1/1*2+1/2*3+1/3*4+1/4*5+......+1/9*10
b,2/1*3+2/3*5+2/5*7+2/7*9+2/9*11
c,3/1*3+3/3*5+3/5*7+3/7*9+3/9*11
d,5/1*3+5/3*5+5/5*7+5/7*9+5/9*11
Giúp mình với
a)\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}\)
= \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{3}{4}+...+\frac{1}{9}-\frac{1}{10}\)
= \(1+\left(\frac{-1}{2}+\frac{1}{2}\right)+\left(\frac{-1}{3}+\frac{1}{3}\right)+...+\left(\frac{-1}{9}+\frac{1}{9}\right)-\frac{1}{10}\)
= \(1-\frac{1}{10}\)
=\(\frac{9}{10}\)
b)\(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}\)
= \(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}\)
=\(1+\left(\frac{-1}{3}+\frac{1}{3}\right)+\left(\frac{-1}{5}+\frac{1}{5}\right)+\left(\frac{-1}{7}+\frac{1}{7}\right)+\left(\frac{-1}{9}+\frac{1}{9}\right)-\frac{1}{11}\)
=\(1-\frac{1}{11}\)
= \(\frac{10}{11}\)
c) đặt A=\(\frac{3}{1.3}+\frac{3}{3.5}+\frac{3}{5.7}+\frac{3}{7.9}+\frac{3}{9.11}\)
\(\frac{1}{3}A\)=\(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}+\frac{1}{9.11}\)
\(\frac{2}{3}A\)=\(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}\)
\(\frac{2}{3}A\)=\(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}\)
\(\frac{2}{3}A\)=\(1+\left(\frac{-1}{3}+\frac{1}{3}\right)+\left(\frac{-1}{5}+\frac{1}{5}\right)+\left(\frac{-1}{7}+\frac{1}{7}\right)+\left(\frac{-1}{9}+\frac{1}{9}\right)-\frac{1}{11}\)
\(\frac{2}{3}A\)=\(\frac{10}{11}\)
A= \(\frac{10}{11}:\frac{2}{3}\)
A= \(\frac{10}{11}.\frac{3}{2}\)=\(\frac{15}{11}\)
d) giả tương tự câu c kết quả \(\frac{25}{11}\)
tổng đặc biệt đó bạn
\(\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+...+\frac{1}{9\times10}\)
\(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}\)
\(1-\frac{1}{10}=\frac{9}{10}\)
những câu sau cũng áp dụng như vậy nhé
\(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}\)
\(=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+.....+\frac{1}{9}-\frac{1}{11}\)
\(=1-\frac{1}{11}=\frac{10}{11}\)
\(\frac{3}{1.3}+\frac{3}{3.5}+\frac{3}{5.7}+\frac{3}{7.9}+\frac{3}{9.11}\)
\(=\frac{3}{2}.\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+....+\frac{1}{9}-\frac{1}{11}\right)\)
\(=\frac{3}{2}.\left(1-\frac{1}{11}\right)=\frac{3}{2}.\frac{10}{11}=\frac{15}{11}\)
Thực hiện phép tính sau có thể
1.12/21-3/7+-2/3
2.-3/5+(-2/5+2)
3.6/7×10/9+1/7×10/9-8/9
4.5/7×5/11+5/7×2/11-5/7×14/11
a) 3^10 . (-5)^21 / (-5)^20 . 3^12
b) -11^5 . 13^7 / 11^5 . 13^8
c) 2^10 . 3^10 - 2^10 . 3^9 / 2^9 . 3^10
d) 5^11. 7^12 + 5^11 . 7^11/5^12 . 7^12 + 9 . 5^11 . 7^11
giúp em với ạ!! Đề bài là rút gọn ạ
2/5-2/9+2/11/7/5-7/9+7/11:1/3-1/4+1/5/7/6-7/8+7/10:tinh nhanh
2/5-2/9+2/11/7/5-7/9+7/11:1/3-1/4+1/5/7/6-7/8+7/10:tính nhanh
a, 7/11 - ( 3/5 + 7/11 )
b, ( 11/22 + 5/11 ) - 19/22
c, 2/9 . 4/5 + 2/9 . 14/5
d, -3/2 . 7/10 -3/2 . 1/10
e, ( 0,75 - 1 + 1/4 ) : ( 1515/1616 + 1616/1717 )
a) \(\frac{7}{11}-\left(\frac{3}{5}+\frac{7}{11}\right)=-\frac{3}{5}\)
b) \(\left(\frac{11}{22}+\frac{5}{11}\right)-\frac{19}{22}=\frac{1}{11}\)
c) \(\frac{2}{9}.\frac{4}{5}+\frac{2}{9}.\frac{14}{5}=\frac{4}{5}\)
d) \(-\frac{3}{2}.\frac{7}{10}-\frac{3}{2}.\frac{1}{10}=-\frac{6}{5}\)
e) \(\left(0,75-1+\frac{1}{4}\right):\left(\frac{1515}{1616}+\frac{1616}{1717}\right)=0\)
-1/9.15/22.-9/25
-2/7.(5/13-9/15)-2/7.8/13
3/10.(-4/9+2/5)-3/10.(5/9+-3/5)
4/11+-5/13+7/11+-8/13
\(a,\frac{-1}{9}.\frac{15}{22}.\frac{-9}{25}\)
\(=\frac{-1.15.\left(-9\right)}{9.22.25}\)
\(=\frac{3}{110}\)
\(b,\frac{-2}{7}.\left(\frac{5}{13}-\frac{9}{15}\right)-\frac{2}{7}.\frac{8}{13}\)
\(=\frac{-2}{7}.\left(\frac{5}{13}+\frac{8}{13}-\frac{3}{5}\right)\)
\(=\frac{-2}{7}.\left(1-\frac{3}{5}\right)\)
\(=\frac{-2}{7}.\frac{2}{5}\)
\(=\frac{-4}{35}\)
\(c,\frac{3}{10}.\left(\frac{-4}{9}+\frac{2}{5}\right)-\frac{3}{10}.\left(\frac{5}{9}-\frac{3}{5}\right)\)
\(=\frac{3}{10}.\left[\left(\frac{-4}{9}+\frac{2}{5}\right)-\left(\frac{5}{9}-\frac{3}{5}\right)\right]\)
\(=\frac{3}{10}.\left(\frac{-4}{9}+\frac{2}{5}-\frac{5}{9}+\frac{3}{5}\right)\)
\(=\frac{3}{10}.\left[\left(\frac{-4}{9}-\frac{5}{9}\right)+\left(\frac{2}{5}+\frac{3}{5}\right)\right]\)
\(=\frac{3}{10}.\left(-1+1\right)\)
\(=\frac{3}{10}.0\)
\(=0\)
\(d,\frac{4}{11}-\frac{5}{13}+\frac{7}{11}-\frac{8}{13}\)
\(=\left(\frac{4}{11}+\frac{7}{11}\right)+\left(\frac{-5}{13}-\frac{8}{13}\right)\)
\(=1-1\)
\(=0\)
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