Tính \(P=1.4.7+4.7.10+...+2021.2024.2027\)
Mình đang cần gấp ạ
\(\frac{2}{1.4.7}+\frac{2}{4.7.10}+...+\frac{2}{58.61.64}\)Mình đag cần gấp. Ai làm nhanh mình tick. Mong mn giúp mình
\(\frac{2}{1.4.7}+\frac{2}{4.7.10}+...+\frac{2}{58.61.64}\)
\(=\frac{1}{3}.\left(\frac{6}{1.4.7}+\frac{6}{4.7.10}+...+\frac{6}{58.61.64}\right)\)
\(=\frac{1}{3}.\left(\frac{7 - 1}{1.4.7}+\frac{10 - 4}{4.7.10}+...+\frac{64 - 58}{58.61.64}\right)\)
\(=\frac{1}{3}.\left(\frac{1}{4}-\frac{1}{4.7}+\frac{1}{4.7}-\frac{1}{7.10}+...+\frac{1}{58.61}-\frac{1}{61.64}\right)\)
\(=\frac{1}{3}.\left(\frac{1}{4}-\frac{1}{61.64}\right)=\frac{1}{3}.\left(\frac{1}{4}-\frac{1}{3904}\right)=\frac{1}{3}.\frac{975}{3904}=\frac{325}{3904}\)
\(\text{Giải :}\)
\(\frac{2}{1.4.7}+\frac{2}{4.7.10}+...+\frac{2}{58.61.64}=\frac{1}{3}.\left(\frac{6}{1.4.7}+\frac{6}{4.7.10}+...+\frac{6}{58.61.64}\right)\)
\(=\frac{1}{3}.\left(\frac{7-1}{1.4.7}+\frac{10-4}{4.7.10}+...+\frac{64-58}{58.61.64}\right)\)
\(=\frac{1}{3}.\left(\frac{1}{4}-\frac{1}{4.7}+\frac{1}{4.7}-\frac{1}{7.10}+...+\frac{1}{58.61}-\frac{1}{61.64}\right)\)
\(=\frac{1}{3}.\left(\frac{1}{4}-\frac{1}{61.64}\right)=\frac{1}{3}.\left(\frac{1}{4}-\frac{1}{3904}\right)=\frac{1}{3}.\frac{975}{3904}=\frac{325}{3904}\)
\(\text{#Hok tốt!}\)
\(\frac{2}{1.4.7}+\frac{2}{4.7.10}+...+\frac{2}{58.61.64}\)Mình đag cần rất gấp. Mọi người giúp mình với. Ai lm nhanh mình tick
\(\frac{2}{1.4.7}+\frac{2}{4.7.10}+...+\frac{2}{58.61.64}\)
\(=\frac{1}{3}\left(\frac{6}{1.4.7}+\frac{6}{4.7.10}+...+\frac{6}{58.61.64}\right)\)
\(=\frac{1}{3}\left(\frac{7-1}{1.4.7}+\frac{10-4}{4.7.10}+...+\frac{64-58}{58.61.64}\right)\)
\(=\frac{1}{3}\left(\frac{1}{1.4}-\frac{1}{4.7}+\frac{1}{4.7}-\frac{1}{7.10}+...+\frac{1}{58.61}-\frac{1}{61.64}\right)\)
\(=\frac{1}{3}\left(\frac{1}{1.4}-\frac{1}{61.64}\right)\)
\(=\frac{325}{3904}\)
Tính A=\(\frac{2}{1.4.7}\)+\(\frac{2}{4.7.10}\)+...+\(\frac{2}{154.157.160}\)
tính nhanh lên nhé mình cần gấp
Tính nhanh:
P=\(\frac{12}{1.4.7}\)+ \(\frac{12}{4.7.10}\)+\(\frac{12}{7.10.13}\)+....+ \(\frac{12}{54.57.60}\)
Giúp e vs e đang cần gấp!!
Đúng em tick cho
\(P=\frac{12}{1.4.7}+\frac{12}{4.7.10}+\frac{12}{7.10.13}+...+\frac{12}{54.57.60}\)
\(P=4.\left(\frac{3}{1.4.7}+\frac{3}{4.7.10}+\frac{3}{7.10.13}+...+\frac{3}{54.57.60}\right)\)
\(P=4\left(\frac{1}{1.4}-\frac{1}{4.7}+\frac{1}{4.7}-\frac{1}{7.10}+\frac{1}{7.10}+...+\frac{1}{54.57}-\frac{1}{57.60}\right)\)
\(P=4.\left(\frac{1}{4}-\frac{1}{3420}\right)\)
\(P=4.\frac{427}{1710}\)
\(P=\frac{854}{855}\)
Tính : 1.4.7 + 4.7.10 +...+ 19.22.25
1.4.7+4.7.10+…+58.61.641.4.7+4.7.10+…+58.61.64
Tính nhanh:
P=12/1.4.7 + 12/4.7.10 + 12/7.10.13 + ... + 12/54.57.60
=2.(6/1.4.7 + 6/4.7.10 + 6/7.10.13 + ... + 6/54.57.60)
=2.(1/1.4-1/4.7+1/4.7-1/7.10+1/7.10-1/10.13+...+1/54.57-1/57.60)
=2(1.4-1/57.60)
TỰ TÍNH
CMR:
A= 1/3 + 1/3 + 1/3 +...+ 1/3 < 1/2
B= 1 + 1/2 + 1/3 + ...+ 1/100 <2
C= 12/ 1.4.7 + 12/ 4.7.10 + ...+ 12/54.57.60 < 1/2
D= 1.2/ 1.4.7 + 1.2/ 4.7.10 +...+ 1.2/ 54.57.60 < 1/2
Lưu ý: C và D là hai đề bài khác nhau nhưng có khi mình chép lộn dấu nên mình mới làm thành hai câu C và D nếu ra đáp án có lẽ mình chép đúng. Tks!!'
Tính \(A=\frac{6}{1.4.7}+\frac{6}{4.7.10}+\frac{6}{7.10.13}+......+\frac{6}{16.19.22}\)
Ta có \(A=\frac{1}{1.4}-\frac{1}{4.7}+\frac{1}{4.7}-\frac{1}{7.10}+\frac{1}{7.10}-...+\frac{1}{16.19}-\frac{1}{19.22}\)
\(=\frac{1}{4}-\frac{1}{418}=\frac{207}{836}\)
\(A=\frac{6}{1\cdot4\cdot7}+\frac{6}{4\cdot7\cdot10}+\frac{6}{7\cdot10\cdot13}+...+\frac{6}{16\cdot19\cdot22}\)
\(A=\frac{1}{1\cdot4}-\frac{1}{4\cdot7}+\frac{1}{4\cdot7}-\frac{1}{7\cdot10}+...+\frac{1}{16\cdot19}-\frac{1}{19\cdot22}\)
\(A=\frac{1}{4}-\frac{1}{19\cdot22}=\frac{207}{836}\)