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vì 1/9 > 1/40 ; 1/29 > 1/40 ; 1/31 > 1/40; 1/39 > 1/40
nên 1/9 + 1/ 29 + 1/31 + 1/39 > 1/40 + 1/40 + 1/40 + 1/40 mà 1/40 + 1/40 + 1/40 + 1/40 = 1/10
=) M > 1/10
M > 1/20 + 1/30 + 1/40 + 1/40
M> 2/15 > 2/20 = 1/10
=> M > 1/10
a,( 3/29 - 1/5 ) x 29/3
=(15/145-29/145)x29/3
=(-14/145)x29/3
=-406/435
=-14/15
b,4 x 11 x 3/4 x 9/121
=4 x 11 x 3x9/1x1x4x121
=1188/484
=59/242
k mk nha
A / ( 3/29 - 1/5 ) x 29/3 = -14/145 x 29/3 = -14/15 B/ 4 x 11 x 3/4 x 9/121 = (4 x 11) x ( 3/4 x 9/121 ) = 44 x 27/484 =27/11 xong rồi đó
dau . la nhan nha em
a) \(\left(\frac{3}{29}-\frac{1}{5}\right).\frac{29}{3}=\frac{29}{3}.\frac{3}{29}-\frac{1}{5}.\frac{29}{3}=1-\frac{29}{15}=\frac{-14}{15}\)
b)\(4.11.\frac{3}{4}.\frac{9}{121}\)
\(=\left(4.\frac{3}{4}\right).\left(11.\frac{9}{121}\right)\)
\(=3.\frac{9}{12}\)
\(=\frac{9}{4}=2\frac{1}{4}\)
a)15/16:3/8x3/4
=15/16:6/16x12/16
=15/16x16/6x12/16
=15/6x12/16
=30/16=15/8
b)5/11x18/29-5/11x8/29+5/11x19/29
=5/11x(18/29-8/29+19/29)
=5/11x1=5/11
29-(10+29)=x-(27-9)
20-10-9=x-27+9
10-9=x-36
1=x-36
x-36=1
x=1+36
x=37
c)
\(\left(1-\frac{1}{2}\right)+\left(1-\frac{1}{6}\right)+....+\left(1-\frac{1}{42}\right)+\left(1-\frac{1}{56}\right)\)
\(\left(1+1+1+....+1+1\right)+\left(\frac{1}{1\times2}+\frac{1}{2\times3}+...+\frac{1}{6\times7}+\frac{1}{7\times8}\right)\)(Có 7 số 1)
\(7+1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}\)
\(7+1-\frac{1}{8}=\frac{63}{8}\)
Gợi ý 1 bài c) còn d) e) cũng làm như vậy nhé
Chúc bạn học tốt !!!
\(M=\frac{1}{2}+\frac{5}{6}+...+\frac{89}{90}=1-\frac{1}{2}+1-\frac{1}{6}+...+1-\frac{1}{90}\)
\(=9-\left(\frac{1}{2}+\frac{1}{6}+...+\frac{1}{90}\right)\)
\(=9-\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{9.10}\right)\)
\(=9-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}\right)\)
\(=9-\left(1-\frac{1}{10}\right)\)
\(=8+\frac{1}{10}\)
\(=\frac{81}{10}\)
\(M=\frac{1}{2}+\frac{5}{6}+...+\frac{89}{90}=1-\frac{1}{2}+1-\frac{1}{6}+...+1-\frac{1}{90}\)
\(=9-\left(\frac{1}{2}+\frac{1}{6}+...+\frac{1}{90}\right)\)
\(=9-\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{9.10}\right)\)
\(=9-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}\right)\)
\(=9-\left(1-\frac{1}{10}\right)\)
\(=8+\frac{1}{10}\)
\(=\frac{81}{10}\)
5/11.18/29-5/11.8/29+5/11-19/29. = -0.19981667035 bạn ạ
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