so sánh M và N: M=4/4.7+4/7.10+4/10.13+....+4/87.90 ; N=10^8+1/10^8-1
Những câu hỏi liên quan
C = 4/4.7 + 4/7.10 + 4/10.13 +....+ 4/73.76
\(\frac{4}{1.4}+\frac{4}{4.7}+\frac{4}{7.10}+\frac{4}{10.13}\)
4/1.4+4/4.7+4/7.10+4/10.13
= 4/3(3/1.4+3/4.7+3/7.10+3/10.13)
=4/3(1/1-1/4+1/4-1/7+1/7-1/10+1/10-1/13)
=4/3(1/1-1/13)
=4/3.12/13
=16/13
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c/m 1/4.7+1/7.10+1/10.13+...+1/604.607 < 1/12
Ta có:
Đặt \(A=\)\(\dfrac{1}{4.7}+\dfrac{1}{7.10}+\dfrac{1}{10.13}+...+\dfrac{1}{604.607}< \dfrac{1}{2}\)
\(=\dfrac{1}{3}.\left(\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{13}+...+\dfrac{1}{604}-\dfrac{1}{607}\right)< \dfrac{1}{2}\)
\(=\dfrac{1}{3}.\left(\dfrac{1}{4}-\dfrac{1}{607}\right)< \dfrac{1}{2}\)
Vì \(\dfrac{1}{3}< \dfrac{1}{2}\) nên \(\dfrac{1}{3}.\left(\dfrac{1}{4}-\dfrac{1}{607}\right)< \dfrac{1}{2}\)
Vậy \(A< \dfrac{1}{2}\)
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............................... =) A < 1/2
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So sánh A và B biết
a,A=6\(\left(x+\frac{1}{3}\right)^2\)
,B=-8-(3,75-x)2
b,A=\(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+\frac{3}{10.13}+\frac{3}{13.16}\)
B=\(\left(\frac{1}{2}\right)^4\)
a)Tính:
3/4.7 + 3/7.10 + 3/10.13 +......+ 3/73.76
b) Tìm x:
x + 4/5.9 +4/9.13 + 4/13.17 +.......+ 4/41.45 = -37/45
Trả lời nhanh giùm mk nhé
Nhanh mk tick
Giải chi tiết ra giùm mk nha
Thanks
1. E = \(\dfrac{3}{1.4}+\dfrac{3}{4.7}+\dfrac{3}{7.10}+\dfrac{3}{10.13}+\dfrac{3}{13.16}+\dfrac{3}{16.19}+\dfrac{3}{19.22}\)
2. (x-4)(x-5)=0
1.
E = \(\dfrac{3}{1.4}\) + \(\dfrac{3}{4.7}\) + \(\dfrac{3}{7.10}\) + \(\dfrac{3}{10.13}\) + \(\dfrac{3}{13.16}\) + \(\dfrac{3}{16.19}\) + \(\dfrac{3}{19.22}\)
E = 1 - \(\dfrac{1}{4}\) + \(\dfrac{1}{4}\) - \(\dfrac{1}{7}\) + \(\dfrac{1}{7}\) - \(\dfrac{1}{10}\) + ... +\(\dfrac{1}{19}\) - \(\dfrac{1}{22}\)
E = 1 - \(\dfrac{1}{22}\)
E = \(\dfrac{21}{22}\)
2.
(x - 4)(x - 5) = 0
TH1:
x - 4 = 0 => x = 4
TH2:
x - 5 = 0 => x = 5
Vậy: x = 4 hoặc x = 5
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Tính
1. 3/4 + 3/4.7 + 3/7.10 + 3/ 10.13 + 3/13.16 + 3/16.19 + 3/19.22 + 3/22.25
2. A = ( 1 - 1/21 ) * ( 1 - 1/28 ) * ( 1 - 1/36 ) *....* ( 1 - 1/1326 )
1: \(A=\dfrac{3}{1\cdot4}+\dfrac{3}{4\cdot7}+...+\dfrac{3}{22\cdot25}\)
\(=1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+...+\dfrac{1}{22}-\dfrac{1}{25}\)
\(=1-\dfrac{1}{25}=\dfrac{24}{25}\)
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(1/1.4+1/4.7+1/7.10+1/10.13+...+1/102.105).x=1
Các bạn giúp m nhanh đc ko ạ! Mình cần gấp!
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ta nhân 3 cả hai vế, được :
\(\left(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{102.105}\right)x=3\)
hay
\(\left(\frac{4-1}{1.3}+\frac{7-4}{4.7}+...+\frac{105-102}{102.105}\right)x=3\) \(\Leftrightarrow\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+..+\frac{1}{102}-\frac{1}{105}\right)x=3\)
\(\Leftrightarrow\left(1-\frac{1}{105}\right)x=3\Leftrightarrow\frac{104}{105}.x=3\Leftrightarrow x=\frac{315}{104}\)
17 tháng 12 2023 lúc 21:43
S=1.4+4.7+7.10+10.13+...+61.64
S = 1.4 + 4.7 + 7.10 + 10.13 + ... + 61.64
1.4.9 = 1.4.(7 + 2) = 1.4.7 + 1.4.2
4.7.9 = 4.7.(10 - 1) = 4.7.10 - 1.4.7
7.10.9 = 7.10.(13 - 4) = 7.10.13 - 4.7.10
10.13.9 = 10.13.(16 - 7) = 10.13.16 - 7.10.13
.......................................................................
61.64.9 = 61.64.(67 - 58) = 61.64.67 - 58.61.64
Cộng vế với vế ta có:
1.4.9 + 4.7.9 + 7.10.9 +...+ 61.64.9 = 1.4.2 + 61.64.67
9(1.4 + 4.7 + 7.10+ ...+ 61.64) = 261576
1.4 + 4.7 + 7.10 +...+ 61.64 = 261576 : 9
1.4 + 4.7 + 7.10 + ... + 61.64 = 29064
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