A=1-1/2+1/3-1/4+...+1/2001-1/2002
A= 1/2003×2002 - 1/2002×2001- 1/2001×2000- .....-1/3×2- 1/2×1
Cho A=1^22+1^32+1^42+....+1^20012+1^20022
Chứng tỏ rằng A <2001^2002
cho n! = 1*2*3*...*n ; tinh
A= (1/2! + 2/3! + 3/4! +...+ 2001/2002!) + 1/2002!
\(A=\left(\frac{2-1}{2!}+\frac{3-1}{3!}+\frac{4-1}{4!}+...+\frac{2002-1}{2002!}\right)+\frac{1}{2002!}\)
\(A=\left(\frac{2}{2!}-\frac{1}{2!}+\frac{3}{3!}-\frac{1}{3!}+\frac{4}{4!}-\frac{1}{4!}+...+\frac{2002}{2002!}-\frac{1}{2002!}\right)+\frac{1}{2002!}\)
\(A=\left(\frac{1}{1!}-\frac{1}{2!}+\frac{1}{2!}-\frac{1}{3!}+\frac{1}{3!}-\frac{1}{4!}+...+\frac{1}{2001!}-\frac{1}{2002!}\right)+\frac{1}{2002!}\)
\(A=\frac{1}{1!}-\frac{1}{2002!}+\frac{1}{2002!}=1\)
A=2000+2001/2001+2002
B1/2+1/3+1/4+1/5+.....1/99+1/100
a) 1 - 2 - 3 + 4 +5 - 6 - 7 + ..... + 2001 - 2002 -2003 + 2004
b) 1 + 2 - 3 - 4 + 5 + 6 - 7 - 8 + ..... + 2001 + 2002 - 2003 - 2004
a) \(1-2-3+4+5-6-7+...+2001-2002-2003+2004\)
\(=\left(1-2-3+4\right)+\left(5-6-7+8\right)+...+\left(2001-2002-2003+2004\right)\)
\(=0+0+...+0=0\)
b) \(1+2-3-4+5+6-7-8+...+2001+2002-2003-2004\)
\(=\left(1+2-3-4\right)+\left(5+6-7-8\right)+...+\left(2001+2002-2003-2004\right)\)
\(=\left(-4\right)+\left(-4\right)+...+\left(-4\right)\)
\(=\left(-4\right)\cdot501=\left(-2004\right)\)
a, chứng minh rằng : 1-1/2+1/3-1/4+...-1/2000+1/2001-1/2002 = 1/1002+ ...+ 1/2002
giúp mk nha
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Câu hỏi của Cristiano Ronaldo - Toán lớp 7 - Học toán với OnlineMath
\(1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+....-\frac{1}{2000}+\frac{1}{2001}-\frac{1}{2002}\)
\(=\left(1+\frac{1}{3}+\frac{1}{5}+......+\frac{1}{2001}\right)-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{6}+...+\frac{1}{2002}\right)\)
\(=\left(1+\frac{1}{2}+\frac{1}{3}+....+\frac{1}{2001}+\frac{1}{2002}\right)-2\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{6}+.....+\frac{1}{2002}\right)\)
\(=\left(1+\frac{1}{2}+\frac{1}{3}+......+\frac{1}{2002}\right)-\left(1+\frac{1}{2}+\frac{1}{3}+......+\frac{1}{1001}\right)\)
\(=\frac{1}{1002}+\frac{1}{1003}+\frac{1}{1004}+.....+\frac{1}{2002}\)
Chúc em học tốt nhé!
giúp mk bài nữa nha
Cho A=1-1/2+1/3-1/4+....+1/2001-1/2002
B=1/1002+1/1003+...+1/2002
Tính A/B=?
\(A=\left(1+\frac{1}{3}+\frac{1}{5}+...+\frac{1}{2001}\right)-\left(\frac{1}{2}+\frac{1}{4}+...+\frac{1}{2002}\right)\)
\(A=\left(1+\frac{1}{3}+\frac{1}{5}+...+\frac{1}{2001}+\frac{1}{2}+\frac{1}{4}+...+\frac{1}{2002}\right)-2.\left(\frac{1}{2}+\frac{1}{4}+...+\frac{1}{2002}\right)\)
\(A=\left(1+\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+\frac{1}{5}+...+\frac{1}{2001}+\frac{1}{2002}\right)-\left(1+\frac{1}{2}+\frac{1}{3}+...+\frac{1}{1001}\right)\)
\(A=\frac{1}{1002}+\frac{1}{1003}+\frac{1}{1004}+...+\frac{1}{2001}+\frac{1}{2002}=B\)
=> A/B = 1
S = 1 - 1/2 + 1/3 - 1/4 + ... + 1/2001 - 1/2002 P = 1/1002 + 1/1003 + ... + 1/2002 Hỏi S - P = ?
S=\(\left(1+\frac{1}{2}+......+\frac{1}{2002}\right)-2.\left(\frac{1}{2}+\frac{1}{4}+..........+\frac{1}{2002}\right)\)
=\(\left(1+\frac{1}{2}+.........+\frac{1}{2002}\right)-\left(1+\frac{1}{2}+.........+\frac{1}{1001}\right)\)
=\(\frac{1}{1002}+\frac{1}{1003}+...........+\frac{1}{2002}=P\)
\(\Rightarrow S-P=0\)
cmr: 1 - 1/2 + 1/3 -1/4 +...-1/200 + 1/2001 - 1/2002 = 1/1002 +...+ 1/2002
AI GIÚP NHÉ!!! THANKS:)