giải phương trình :
1/(16√17+17√16)+1/(17√18+18√17)+1/(18√19+19√18)+⋯+1/(x√(x+1)+(x+1)√x)=499/2012
Những câu hỏi liên quan
chứng minh rằng:\(\frac{17^{18}+1}{17^{19}+1}< \frac{17^{18}+1+16}{17^{19}+1+16}\)
-5 phan14 và 30 phân -84 có bằng nhau không tại sao
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(1 + 1/16) x (1 + 1/17) x (1 + 1/18) x (1 + 1/19) x (1 + 1/20) = ?
x+1/19+x+2/18+x+3/17+x+4/16=4
\(x+\frac{1}{19}+x+\frac{2}{18}+x+\frac{3}{17}+x+\frac{4}{16}=4\)
\(4x+\left(\frac{1}{19}+\frac{2}{18}+\frac{3}{17}+\frac{4}{16}\right)=4\)
\(4x+\frac{6863}{11628}=4\)
\(4x=4-\frac{6863}{11628}=\frac{39649}{11628}\)
\(\Rightarrow x=\frac{39649}{11628\cdot4}=\frac{39649}{46512}\)
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X = 21 - 20 + 19 - 18 + 17 -16 ........ + 1
X = 21 - 20 + 19 - 18 + 17 - 16 ........ + 1
X = 1 + 1 + 1 + ........ + 1
X = 11
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105 * x- 20-18-16-.....-2=19+17+15+.......+1
=> 105 x X + (-70) = 100
105 x X = 170
x = 170 : 105 = 34/21
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x = 21 - 20 + 19 - 18 +17 -16 .... +1
tim x =
x = 21 - 20 + 19 - 18 +17 -16 .... +1
=> x=(21-20)+(19-18)+......+(3-2)+1
=> x= 1+1+........+1+1
11 số hạng
=> x=1x11
=> x=11
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Tính nhanh:
11 x 12 + 12 x 13 + 13 x 14 + 14 x 15 + 15 x 16 + 16 x 17 + 17 x 18 + 18 x 19 + 19 x 20 + 20 x 21
11 x 12 + 12 x 13 + 13 x 14 + 14 x 15 + 15 x 16 + 16 x 17 + 17 x 18 + 18 x 19 + 19 x 20 + 20 x 21
= 12 x ( 11 + 13 ) + 14 x ( 13 + 15 ) + 16 x ( 15 + 17 ) + 18 x ( 17 + 19 ) + 20 x 21
= 12 x 24 + 14 x 28 + 16 x 32 + 18 x 36 + 420
= 288 + 392 + 512 + 648 + 420
= ( 288 + 392 ) + ( 512 + 648 ) + 420
= 680 + 1160 + 420
= 1840 + 420
= 2260
tk nha
=
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Ta có:
11 x 12 + 12 x 13 + 13 x 14 + 14 x 15 + 15 x 16 + 16 x 17 + 17 x 18 + 18 x 19 + 19 x 20 + 20 x 21
= 12 x ( 11 + 13 ) + 14 x ( 13 + 15 ) + 16 x ( 15 + 17 ) + 18 x ( 17 + 19 ) + 20 x 21
= 12 x 24 + 14 x 28 + 16 x 32 + 18 x 36 + 420
= 288 + 392 + 512 + 648 + 420
= ( 288 + 392 ) + ( 512 + 648 ) + 420
= 680 + 1160 + 420
= 1840 + 420
= 2260
#Mạt Mạt#
11 x 12 + 12 x 13 + 13 x 14 + 14 x 15 + 15 x 16 + 16 x 17 + 17 x 18 + 18 x 19 + 19 x 20 + 20 x 21
= 12 x ( 11 + 13 ) + 14 x ( 13 + 15 ) + 16 x ( 15 + 17 ) + 18 x ( 17 + 19 ) + 20 x ( 19 + 21 )
= 12 x 24 + 14 x 28 + 16 x 32 + 18 x 36 + 20 x 40
= 288 + 392 + 512 + 648 + 800
= ( 288 + 392 ) + ( 512 + 648 ) + 800
= 680 + 1160 + 800
= 2640
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tính nhanh
25/37 x 18/29 + 18/29 x 12/37
31/85 x 11/19 + 31/85 x 12/19 - 42/19 x 31/85
c , 16/53 : 17/9 - 16/53 : 17/8
1/5 x 12/31 x 4/3 + 19/31 x 4/15
a) \(\dfrac{25}{37}\times\dfrac{18}{29}+\dfrac{18}{29}\times\dfrac{12}{37}\)
\(=\dfrac{18}{29}\times\left(\dfrac{25}{37}+\dfrac{12}{37}\right)\)
\(=\dfrac{18}{29}\times\dfrac{37}{37}\)
\(=\dfrac{18}{29}\times1\)
\(=\dfrac{18}{29}\)
b) \(\dfrac{31}{85}\times\dfrac{11}{19}+\dfrac{31}{85}\times\dfrac{12}{19}-\dfrac{42}{19}\times\dfrac{31}{85}\)
\(=\dfrac{31}{85}\times\left(\dfrac{11}{19}+\dfrac{12}{19}-\dfrac{42}{19}\right)\)
\(=\dfrac{31}{85}\times\dfrac{-19}{19}\)
\(=\dfrac{31}{85}\times-1\)
\(=-\dfrac{31}{85}\)
c) \(\dfrac{16}{53}:\dfrac{17}{9}-\dfrac{16}{53}:\dfrac{17}{8}\)
\(=\dfrac{16}{53}:\left(\dfrac{9}{17}-\dfrac{8}{17}\right)\)
\(=\dfrac{16}{53}:\dfrac{1}{17}\)
\(=\dfrac{16}{901}\)
c) \(\dfrac{1}{5}\times\dfrac{12}{31}\times\dfrac{4}{3}+\dfrac{19}{31}\times\dfrac{4}{15}\)
\(=\dfrac{4}{15}\times\dfrac{12}{31}+\dfrac{19}{31}\times\dfrac{4}{15}\)
\(=\dfrac{4}{15}\times\left(\dfrac{12}{31}+\dfrac{19}{31}\right)\)
\(=\dfrac{4}{15}\times\dfrac{31}{31}\)
\(=\dfrac{4}{15}\times1\)
\(=\dfrac{4}{15}\)
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a: =18/29*(25/37+12/37)
=18/29
b: =31/85(11/19+12/19-42/19)
=-31/85
c; =16/53(9/17+8/17)=16/53
d: =4/15(12/31+19/31)=4/15
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16, giải phương trình.
1, \(\frac{x+5}{65}+\frac{x+10}{60}=\frac{x+15}{55}+\frac{x+20}{50}\)
2, \(\frac{x+91}{81}+\frac{x+92}{82}+\frac{x+93}{83}=3\)
3, \(\frac{59-x}{19}+\frac{58-x}{18}=\frac{57-x}{17}+\frac{56-x}{16}\)
4, \(\frac{x}{15}+\frac{x+1}{16}+\frac{x+2}{17}+\frac{x+3}{18}+\frac{x+4}{19}=5\)
