tinh nhanh
a,5/13+5/17+ -20/41+8/13+ -21/41
b,53/117.129/311+53/117.43/311- -64/117.172/311
c,C=[-1/7]:2/3+[-1/7]:2
d,D=1/3.5+1/5.7+1/7.9+1/9.11+1/11.13+1/13.15
ai nhanh minh tick cho
Câu 1:
a) Tính giá trị biểu thức sau: A=(-1).(-1)^2.(-1)^3.(-1)^4.....(-1)^2010.(-1)^2011
b)Tính nhanh: B= 13/3+13/3.5+13/5.7+13/7.9+13/9.11+13/11.13
Giúp mình với nhaa!!! Thanks mn!!!
Bài 1.Tính bằng cách hớp lí
a,(1/4+-5/13)+(2/11+-8/13+3/4)
b,(21/31+-16/7)+(44/53+10/31)+9/53
c,-5/7+3/4+-1/5+-2/7+1/4
d,-3/27+-6/17+1/25+-28/31+-11/17+-1/5
Bài 2.Tính tổng
A=1/1.2+1/2.3+1/3.4+......+1/2003.2004
AI LÀM NHANH VÀ ĐÚNG MK TICK NHA
Bài 1: Ta chỉ cần bỏ ngoặc rồi cộng hai phân số để ra kết quả là số tự nhiên là xong
Bài 2:
A = \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+............+\frac{1}{2003.2004}\)
A = \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-.............-\frac{1}{2003}+\frac{1}{2003}-\frac{1}{2004}\)
A = \(1-\frac{1}{2004}\)
A = \(\frac{2004}{2004}-\frac{1}{2004}=\frac{2003}{2004}\)
Mk làm mẫu 1 bài nha
Bài 1 :
a, = (1/4+3/4) - (5/13+8/13)+2/11
= 1 - 1 + 2/11
= 2/11
Tk mk nha
\(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{2003.2004}\)
\(\Leftrightarrow A=1\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{2003}-\frac{1}{2004}\right)\)
\(\Leftrightarrow A=1\left(1-\frac{1}{2004}\right)\)
\(\Leftrightarrow A=\frac{2003}{2004}\)
B=1/3.5+1/5.7+1/7.9+1/9.11+1/11.13
Tinh B
\(\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}+\frac{1}{9.11}+\frac{1}{11.13}\)
\(=\frac{1}{2}\left(\frac{5-3}{3.5}+\frac{7-5}{5.7}+\frac{9-7}{7.9}+\frac{11-9}{9.11}+\frac{13-11}{11.13}\right)\)
\(=\frac{1}{2}\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+\frac{1}{11}-\frac{1}{13}\right)\)
\(=\frac{1}{2}\left(\frac{1}{3}-\frac{1}{13}\right)=\frac{5}{39}\)
A=6/1.3.7 + 6/3.7.9 + 6/7.9.13 + 6/9.13.15 + 6/13/15/19
Giup mk nhé và làm theo cách dưới :
C=4/1.3.5 + 4/3.5.7 + 4/5.7.9 + 4/7.9.11 + 4/9.11.13
C=5-1/1.3.5 + 7-3 /3.5.9 + ............................ + 13-9/9.11.13
C=5/1.3.5 - 1/1.3.5 + 7/3.5.7 - 3/3.5.7 + ................... + 13/9.11.13 - 9/9.11.13
C=1/1.3 -1/3.5 + 1/3.5- 1/5.7 + ................................. + 1/9.11 - 1/11.13
C=1/1.3 - 1/11.13
C= 11.13/3.11.13 - 3/3.11.13
C=140/425
mình cũng ko hiểu cách giải này cho lắm nên mình làm thế thôi
1) \(\dfrac{5}{13}\) +\(\dfrac{-5}{17}\) + \(\dfrac{-20}{41}\) + \(\dfrac{8}{13}\) +\(\dfrac{-21}{41}\)
2) \(\dfrac{1}{5}\) + \(\dfrac{-2}{9}\) + \(\dfrac{-7}{9}\) + \(\dfrac{4}{5}\) +\(\dfrac{16}{17}\)
3) \(\dfrac{2}{3.5}\) + \(\dfrac{2}{5.7}\) +\(\dfrac{2}{7.9}\) +....................+ \(\dfrac{2}{99.101}\)
1: =5/13+8/13-20/41-21/41-5/17
=1-1-5/17=-5/17
2: =1/5+4/5-2/9-7/9+16/17
=16/17+1-1=16/17
3: =1/3-1/5+1/5-1/7+...+1/99-1/101
=1/3-1/101
=98/303
a,\(\frac{-5}{9}+\frac{8}{15}+\frac{-2}{11}+\frac{4}{-9}+\frac{7}{15}\)
b,\(\frac{5}{13}+\frac{-5}{17}+\frac{-20}{41}+\frac{8}{13}+\frac{-21}{41}\)
c,\(\frac{1}{5}+\frac{-2}{9}+\frac{-7}{9}+\frac{4}{5}+\frac{16}{17}\)
d,\(\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+......+\frac{2}{99.101}\)
a,\(=\frac{-5}{9}+\frac{8}{15}+\frac{-2}{11}+\frac{-4}{9}+\frac{7}{15}\)
\(\left(\frac{-5}{9}+\frac{-4}{9}\right)+\left(\frac{8}{15}+\frac{7}{15}\right)+\frac{-2}{11}\)
=-1+1+-2/11
=0+-2/11
=-2/11
b,\(=\left(\frac{5}{13}+\frac{8}{13}\right)+\left(\frac{-20}{41}+\frac{-21}{40}\right)+\frac{-5}{17}\)
=1+-1+-5/17
=0+-5/17
=-5/17
c,\(=\left(\frac{1}{5}+\frac{4}{5}\right)+\left(\frac{-2}{9}+-\frac{7}{9}\right)+\frac{16}{17}\)
=1+-1+16/17
=0+16/17
=16/17
d,\(=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{99}-\frac{1}{101}\)
\(=\frac{1}{3}-\frac{1}{101}=\frac{98}{303}\)
a.\(\frac{-5}{9}\)+\(\frac{8}{15}\)+\(\frac{-2}{11}\)+\(\frac{4}{-9}\)+\(\frac{7}{15}\)
=\(\frac{-5}{9}\)+\(\frac{4}{-9}\)+\(\frac{8}{15}\)+\(\frac{7}{15}\)+\(\frac{-2}{11}\)
=(\(\frac{-5}{9}\)+\(\frac{-4}{9}\))+(\(\frac{8}{15}\)+\(\frac{7}{15}\))+\(\frac{-2}{11}\)
=(-1)+1+\(\frac{-2}{11}\)
=0+\(\frac{-2}{11}\)
=\(\frac{-2}{11}\).
1) Tìm x
a) (1/4 x X - 1/8) x 3/4 = 1/4
b) 12/5 : X = 14/3 x 4/7
c) x + 2/3 = 8 : 4 - 1
2) Thực hiện phép tính:
a) (1/5 + 3/4) x 1/2
b) 13/20 - (1/4 - 5/20)
c) 1/10 + 4/20 + 9/30 + 25/50 + 36/60 + 49/70 + 64/80 + 81/90
d) 2/3.5 + 2/5.7 + 2/7.9 + ... + 2/41.43
Tính nhanh
a) 31/23 - (7/32 + 8/23)
b) 38/45 - (8/45 - 17/51 - 3/11)
c)(1/3 + 12/67 + 13/41) - ( 79/67 - 28/41)
d) 1/5 + -1/6 + 1/7 + -1/8 + 1/9 + 1/8 + -1/7 + 1/6 + -1/5
Tính nhanh
a) 31/23 - (7/32 + 8/23)
b) 38/45 - (8/45 - 17/51 - 3/11)
c)(1/3 + 12/67 + 13/41) - ( 79/67 - 28/41)
d) 1/5 + -1/6 + 1/7 + -1/8 + 1/9 + 1/8 + -1/7 + 1/6 + -1/5
`a,`
`31/23-(7/32+8/23)`
`=31/23-7/32-8/23`
`=(31/23-8/23)-7/32`
`=1-7/32=25/32`
`b,`
`38/45-(8/45-17/51-3/11)`
`=38/45-8/45+17/51+3/11`
`= (38/45-8/45)+17/51+3/11`
`=2/3+17/51+3/11`
`=1+3/11=14/11`
`c,`
`(1/3+12/67+13/41)-(79/67-28/41)`
`= 1/3+12/67+13/41-79/67+28/41`
`= 1/3+(12/67-79/67)+(13/41+28/41)`
`= 1/3+(-1)+1=1/3+(-1+1)=1/3+0=1/3`
`d,`
`1/5+(-1/6)+1/7+(-1/8)+1/9+1/8+(-1/7)+1/6+(-1/5)`
`= (1/5+ -1/5)+(-1/6+1/6)+(1/7+ -1/7)+(-1/8 +1/8)+1/9`
`= 0+0+0+0+1/9=1/9 .`