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7 tháng 7 2017
a) Ta thấy \(\frac{1}{2}< \frac{2}{3};\frac{3}{4}< \frac{4}{5};...;\frac{99}{100}< \frac{100}{101}\)
\(\Rightarrow A=\frac{1}{2}.\frac{3}{4}.\frac{5}{6}...\frac{99}{100}< B=\frac{2}{3}.\frac{4}{5}.\frac{6}{7}...\frac{100}{101}\)
b) \(A.B=\left(\frac{1}{2}.\frac{3}{4}.\frac{5}{6}...\frac{99}{100}\right).\left(\frac{2}{3}.\frac{4}{5}.\frac{6}{7}...\frac{100}{101}\right)\)
\(A.B=\frac{1.\left(3.5...99\right).\left(2.4.6...100\right)}{\left(2.4.6...100\right).\left(3.5.7...99\right).101}=\frac{1}{101}\)
c) vì A < b nên A . A < A . B < \(\frac{1}{101}< \frac{1}{100}\)
do đó : A . A < \(\frac{1}{10}.\frac{1}{10}\)suy ra A < \(\frac{1}{10}\)
10 tháng 3 2022
\(1-2-3+4+5-6-7+8+...+97-98-99+100+101\)
\(=\left(1-2-3+4\right)+\left(5-6-7+8\right)+...+\left(97-98-99+100\right)+101\)
\(=0+0+...+0+101\)
\(=101\)
DD
9 tháng 11 2016
số các số hạng là
( 100 - 1):1+1=100 ( so )
tổng 1+2+3+4+.........+100 la
( 1+100) x100 : 2=5050
D/s: 5050
LN
26 tháng 6 2018
a) 1+2+3+...+2018
=[(2018-1):1+1].(2018+1):2
=2018.2019:2
=2037171
b) 4+7+10+13+...+2017
=[(2017-4):3+1].(2017+4):2
=672.2021:2
=679056
c) 1+2-3-4+5+6-7-8+9+10-11-12+13+14
=(1+2-3-4)+(5+6-7-8)+(9+10-11-12)+13+14
=-4+(-4)+(-4)+13+14
=-12+27
=15
d) 23 x 75 + 25 x 23 + 180
=23 x (75+25) +180
=23 x 100 +180
=2300+180
2480
chúc ban hoc tốt nha
26 tháng 6 2018
a) Số số hạng: ( 2018 - 1 ) : 1 + 1 = 2018
Tổng: 2018 x ( 2018 + 1 ) : 2 = 2 037 171
31 tháng 8 2016
số đó là
45+5+90+10
=50+100
=150
10+100+93+5+2
=110+100
=210
ủng hộ nhé
J
2
DN
6 tháng 9 2018
\(\frac{1}{3}+\frac{1}{4}+\frac{1}{5}+\frac{8}{10}+\frac{26}{39}+\frac{75}{100}\)
\(=\frac{1}{3}+\frac{1}{4}+\frac{1}{5}+\frac{4}{5}+\frac{2}{3}+\frac{3}{4}\)
\(=\left(\frac{1}{3}+\frac{2}{3}\right)+\left(\frac{1}{4}+\frac{3}{4}\right)+\left(\frac{1}{5}+\frac{4}{5}\right)\)
\(=1+1+1\)
\(=3\)
6 tháng 9 2018
1/3 + 1/4 + 1/5 + 8/10 + 26/39 + 75/100
= 7/12 + 1/5 + 8/10 + 26/39 +75/100
= 47/60 + 8/10 + 26/39 + 75/100
= 19/12 + 26/39 + 75/100
= 52/ 117 + 75/100
= 559/400
NH
8
TN
20 tháng 6 2018
Số số hạng là:
( 100 - 2 ) : 2 + 1 = 50
Tổng là:
( 100 + 2 ) x 50 : 2 = 2550
Đáp số: 2550
a : 12.03
b : 23.45
dung 999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999% luôn đó
10+2+3/100
=10+2+0,03
=12+0,03
=12,03
23+4/10+5/100
=23+0,4+0,05
=23,4+0,05
=23,45