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\(S=\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{40.43}+\frac{3}{43.46}\)
\(S=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{40}-\frac{1}{43}+\frac{1}{43}-\frac{1}{46}\)
\(S=1-\frac{1}{46}< 1\)
Chứng tỏ S < 1
Ủng hộ mk nha ^_^
S = \(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+......+\frac{3}{43.46}\)
\(=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+.....+\frac{1}{43}-\frac{1}{46}\)
\(=1-\frac{1}{46}=\frac{45}{46}< 1\)
\(\frac{7}{3}\)+ \(\frac{11}{2}\)- \(\frac{1}{5}\)= \(\frac{70}{30}\)+ \(\frac{165}{30}\)- \(\frac{6}{30}\)
= \(\frac{235}{30}\)- \(\frac{6}{30}\)
= \(\frac{229}{30}\)
\(\frac{11}{4}\)x \(\frac{2}{33}\)- \(\frac{1}{40}\)= \(\frac{22}{132}\)- \(\frac{1}{40}\)
= \(\frac{17}{120}\)
= 1 -1/4 +1/4 -1/7 +1/7 -1/10+...+1/40 -1/43 +1/43 -1/46
= 1 -1/46
= 45/46
\(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{40.43}+\frac{3}{43.46}\)
\(=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{40}-\frac{1}{43}+\frac{1}{43}-\frac{1}{46}\)
\(=1-\frac{1}{46}\)
\(=\frac{45}{46}\)
_Chúc bạn học tốt_
1.\(\frac{4}{3.7}+\frac{4}{7.11}+\frac{4}{11.15}+\frac{4}{15.19}+\frac{4}{19.23}+\frac{4}{23.27}\)
\(=\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+...+\frac{4}{23}-\frac{4}{27}\)
\(=\frac{1}{3}-\frac{1}{27}=\frac{9}{27}-\frac{1}{27}=\frac{8}{27}\)
2. Đặt \(A=\frac{3}{14}+\frac{3}{84}+\frac{3}{204}+\frac{3}{374}+\frac{3}{594}+\frac{3}{864}\)
\(\Rightarrow A=\frac{3}{2.7}+\frac{3}{7.12}+...+\frac{3}{27.32}\)
\(\Rightarrow5A=3.\left(\frac{5}{2.7}+\frac{5}{7.12}+...+\frac{5}{27.32}\right)\)
\(\Rightarrow5A=3.\left(\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{12}+...+\frac{1}{27}-\frac{1}{32}\right)\)
\(\Rightarrow5A=3.\left(\frac{1}{2}-\frac{1}{32}\right)\)
\(\Rightarrow5A=3.\frac{15}{32}=\frac{45}{32}\Rightarrow A=\frac{45}{32}:5=\frac{9}{32}\)
3. Đặt \(S=\frac{1}{10}+\frac{1}{40}+\frac{1}{88}+...+\frac{1}{340}\)
\(\Rightarrow3S=\frac{3}{10}+\frac{3}{40}+...+\frac{3}{340}\)
\(\Rightarrow3S=\frac{3}{2.5}+\frac{3}{5.8}+...+\frac{3}{17.20}\)
\(\Rightarrow3S=\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{17}-\frac{1}{20}\)
\(\Rightarrow3S=\frac{1}{2}-\frac{1}{20}=\frac{9}{20}\Rightarrow S=\frac{9}{20}:3=\frac{3}{20}\)
Câu 1:
\(\frac{4}{3.7}+\frac{4}{7.11}+\frac{4}{11.15}+\frac{4}{15.19}+\frac{4}{19.23}+\frac{4}{23.27}\)
\(\Rightarrow\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{15}+\frac{1}{15}-\frac{1}{19}+\frac{1}{19}-\frac{1}{23}+\frac{1}{23}-\frac{1}{27}\)
\(\Rightarrow\frac{1}{3}-\frac{1}{27}\)
\(=\frac{8}{27}\)
mk bt làm mỗi 1 câu thui thông cảm
B) 37 x 62 + 37 x 38
37 x ( 62+38)
37 x 100
3700
hok tốt
a, 59 + 532 + 267 + 268 + 733
= 59 + ( 532 + 268 ) + ( 267 + 733 )
= 59 + 800 + 1000
= 859 + 1000
= 1859
b, 37 × 62 + 37 × 38
= 37 × ( 62 + 38 )
= 37 × 100
= 3 700
c, ( 1356 + 845 ) - ( 356 + 645 )
= 1356 + 845 - 356 - 645
= ( 1356 - 356 ) + ( 845 - 645 )
= 1000 + 200
= 1 200
Số số hạng của dãy:
(1000 - 1) : 3 + 1 = 334
Tổng là:
(1000 + 1) . 334 : 2 = 167167
Dễ SSH :
( 1000 - 1 ) : 3 + 1 = 334
Tổng :
( 1000 + 1 ) x 334 : 2 = tự tính
Câu hỏi của Phí Hải Anh - Toán lớp 5 - Học toán với OnlineMath
Mình nãy trả lời sai hả bạn?
a) 59 + 532 + 267 + 268 + 733
=59+(532+268)+(267+733)
=59+800+1000
=859+1000
=1869
b) 37 × 62 + 37 × 38
=37x(62+38)
=37x100
=3700
c ( 135 + 845 ) - ( 356 + 645 )
=135+845-356+645
=(135+845+645)-356
=1625-365
=1260
d)4 × 37 × 25 × 3 × 7
=(4x25)x(7x3)x37
=100x21x37
=2100x37
=77700
e) 14, 7 × 4 + 52,8 + 14,7 × 6 + 47,2
=14,7x(4+6)x(47,2+52,8)
=14,7x10x100
=147x100
=14700
d) ( 675,75 : 25 + 2255 : 11 ) - 216, 8
=27.03+250-216,8
=277.03-216.8
=60.23
Nhớ k cho mk nhé