biet n!=1.2.3...5.1:1!+2:2!+3:3!+4:4!+5:5!=
Những câu hỏi liên quan
biet n!=1.2.3....n.tinh 1. 1 ! +2 . 2 ! +3 . 3 ! +4 . 4 !+ 5 . 5 ! =.................................
Cau 1: Tim n biet : 5/8 + 5/24 + 5/48 + 5/80 + ... + 5/2n + 2 . 2n + 4 = 189/112
Cau 2 : Cho A = 1 + 1/1.2 + 1/1.2.3 + ... + 1/1.2.3...2014. So sanh A voi 2
Cau 3 : Tim n biet : 5/3 + 5/15 + 5/35 + 5/63 +...+ 5/2n + 1 . 2n + 3 = 172/69
a) -3/5.1/2+1/5.1/2-1/3/5.1/2
b) -2/5.1/3-1/3:5/2
c) -3/5-1/1/4 . -12/25
đ) 1/2.3+1/3.4+1/5.6+...+1/99.100
1^5-5.1^4+5.1^3+5.x^2 -6.1
Thực hiện phép tính ( tính nhanh nếu có thể )
1, 11 3/13-(2 4/7+5 3/13)
2, 19 5/8:7/12+(-15 1/4):7/12
3, 2/5.1/3-2 2/15:1/5+3/5.1/3
4, (3 1/3+2,5):(3 1/6-4 1/5)-11/31
5, 75%-1 1/5+0,5:5/12-(-1/2)2
Bài làm
1.
11 3/13 - ( 2 4/7 + 5 3/13 )
= 11 3/13 - 2 4/7 - 5 3/13
= ( 11 3/13 - 5 3/13 ) - 2 4/7
= { (11 - 5 ) . ( 3/13 - 3/13 ) } - 2 4/7
= ( 6 . 0 ) - 2 4/7
= 0 - 2 4/7
= 2 4/7
= 18/7
2 .
19 5/8 : 7/12 + ( -15 1/4) : 7/12
= { 19 5/8 + ( -15 1/4 ) } : 7/12
= [ { 19 + ( - 15) } . ( 5/8 + 1/4 ) ] : 7/12
= { 4 . ( 5/8 + 2/8 ) } : 7/12
= ( 4 . 7/8 ) : 7/12
= 1.7/2 : 7/12
= 7/2 : 7/12
= 7/2 . 12/7
= 1.1/6.1
= 1/6
3 .
2/5 . 1/3 - 2 2/15 : 1/5 + 3/5 . 1/3
= 1/3 . ( 2/5 + 3/5 ) - 2 2/15 : 1/5
= 1/3 . 5/5 - 32/15 . 5/1
= 1/3 . 1 - 32.1/3.1
= 1/3 - 32/3
= -31/3
4 .
( 3 1/3 + 2,5 ) : ( 3 1/6 - 4 1/5 ) - 11/31
= ( 10/3 + 25/10 ) : { ( 3 - 4 ) . ( 1/6 - 1/5 ) - 11/31
= ( 10/3 + 5/2 ) : { (-1) . ( 5/30 - 6/30 ) } - 11/31
= ( 20/6 + 15/6 ) : { (-1) . (-1)/30 } - 11/31
= 35/6 : 1/30 - 11/31
= 35/6 . 30/1 - 11/31
= 35.5/1.1 - 11/31
= 175 - 11/31
= 5425/31 - 11/31
= 5414/31
5.
75% - 1 1/5 + 0,5 : 5/12 - (-1/2)2
= 75/100 - 6/5 + 5/12 - 1/4
= 3/4 - 6/5 + 5/12 - 1/4
= ( 3/4 - 1/4 ) + ( 5/12 - 6/5 )
= 2/4 + ( 25/60 - 30/60 )
= 1/2 + (-5)/60
= 1/2 + (-1)/12
= 6/12 + (-1)/12
= 5/12
Đúng thì k cho mình nha !
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1)
11 3/13 - ( 2 4/7 + 5 3/13 )
= 11 3/13 - 2 4/7 - 5 3/13
= ( 11 3/13 - 5 3/13 ) - 2 4/7
= { (11 - 5 ) . ( 3/13 - 3/13 ) } - 2 4/7
= ( 6 . 0 ) - 2 4/7
= 0 - 2 4/7
= 2 4/7
= 18/7
2 )
19 5/8 : 7/12 + ( -15 1/4) : 7/12
= { 19 5/8 + ( -15 1/4 ) } : 7/12
= [ { 19 + ( - 15) } . ( 5/8 + 1/4 ) ] : 7/12
= { 4 . ( 5/8 + 2/8 ) } : 7/12
= ( 4 . 7/8 ) : 7/12
= 1.7/2 : 7/12
= 7/2 : 7/12
= 7/2 . 12/7
= 1.1/6.1
= 1/6
3 )
2/5 . 1/3 - 2 2/15 : 1/5 + 3/5 . 1/3
= 1/3 . ( 2/5 + 3/5 ) - 2 2/15 : 1/5
= 1/3 . 5/5 - 32/15 . 5/1
= 1/3 . 1 - 32.1/3.1
= 1/3 - 32/3
= -31/3
4 )
( 3 1/3 + 2,5 ) : ( 3 1/6 - 4 1/5 ) - 11/31
= ( 10/3 + 25/10 ) : { ( 3 - 4 ) . ( 1/6 - 1/5 ) - 11/31
= ( 10/3 + 5/2 ) : { (-1) . ( 5/30 - 6/30 ) } - 11/31
= ( 20/6 + 15/6 ) : { (-1) . (-1)/30 } - 11/31
= 35/6 : 1/30 - 11/31
= 35/6 . 30/1 - 11/31
= 35.5/1.1 - 11/31
= 175 - 11/31
= 5425/31 - 11/31
= 5414/31
5)
75% - 1 1/5 + 0,5 : 5/12 - (-1/2)2
= 75/100 - 6/5 + 5/12 - 1/4
= 3/4 - 6/5 + 5/12 - 1/4
= ( 3/4 - 1/4 ) + ( 5/12 - 6/5 )
= 2/4 + ( 25/60 - 30/60 )
= 1/2 + (-5)/60
= 1/2 + (-1)/12
= 6/12 + (-1)/12
= 5/12
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Xem thêm câu trả lời
Tính giá trị biểu thức
a) 2/5.1/3-2/15:1/5+3/5.1/3
b) 4/2.4+4/4.6+4/6.8+....+4/2008.2010
\(\frac{2}{5}:\frac{1}{3}-\frac{2}{15}:\frac{1}{5}+\frac{3}{5}.\frac{1}{3}\)
\(=\frac{6}{5}+\frac{-2}{3}+\frac{1}{5}\)
\(=\frac{11}{15}\)
~ Hok tốt ~
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\(\frac{4}{2.4}+\frac{4}{4.6}+\frac{4}{6.8}+...+\frac{4}{2008.2010}\)
\(=4.\left(\frac{1}{2.4}+\frac{1}{4.6}+\frac{1}{6.8}+...+\frac{1}{2008.2010}\right)\)
\(=4.\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{2008}-\frac{1}{2010}\right)\)
\(=4.\left[\frac{1}{2}+\left(\frac{1}{4}-\frac{1}{4}\right)+\left(\frac{1}{6}-\frac{1}{6}\right)+\left(\frac{1}{8}-\frac{1}{8}\right)+...+\left(\frac{1}{2008}-\frac{1}{2008}\right)-\frac{1}{2010}\right]\)
\(=4.\left[\frac{1}{2}-\frac{1}{2010}\right]\)
\(=4.\frac{502}{1005}=\frac{2008}{1005}\)
~ Hok tốt ~
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b, \(\frac{4}{2.4}+\frac{4}{4.6}+\frac{4}{6.8}+...+\frac{4}{2008.2010}\)
\(=2\left(\frac{2}{2.4}+\frac{2}{4.6}+\frac{2}{6.8}+...+\frac{2}{2008.2010}\right)\)
\(=2\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{2008}-\frac{1}{2010}\right)\)
\(=2\left(\frac{1}{2}-\frac{1}{2010}\right)\)
\(=2.\frac{502}{1005}\)
\(=\frac{1004}{1005}\)
Study well ! >_<
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3x.(1/1.1/2+1/2.1/3+1/3.1/4+1/4.1/5+1/5.1/6)=3/4
biet n! =1*2**3*...*n . tinh 1*1!+2*2!+3*3!+4*4!+5*5!=?
Có trong Violympic Toán vòng 3 đó đáp án là 719 nha !!!
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Tính hợp lí nếu có thể :
56 : 54 + 23. 22 -225 : 152
7/19 . 8/113/11 .7/19 . -12/19
-7/25 . 39/ 14 . 50/78
(3/8 +-3/4 +7/12):5/6+1/2
2/5.1/3-2/15:1/5+3/5.1/3
a: \(=5^2+2^5-1=25+32-1=25+31=56\)
c: \(=\dfrac{-7}{25}\cdot\dfrac{39}{14}\cdot\dfrac{50}{78}\)
\(=\dfrac{-7}{14}\cdot\dfrac{39}{78}\cdot\dfrac{50}{25}=\dfrac{-1}{2}\)
d: \(=\left(\dfrac{3}{8}-\dfrac{3}{4}+\dfrac{7}{12}\right)\cdot\dfrac{6}{5}+\dfrac{1}{2}\)
\(=\dfrac{9-18+14}{24}\cdot\dfrac{6}{5}+\dfrac{1}{2}\)
\(=\dfrac{1}{4}+\dfrac{1}{2}=\dfrac{3}{4}\)
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