\(-\frac{4}{1.2}-\frac{4}{2.3}-\frac{4}{3.4}-...-\frac{4}{98.99}\)
\(=-4\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{98.99}\right)\)
\(=-4\left(\frac{2-1}{1.2}+\frac{3-2}{2.3}+...+\frac{99-98}{98.99}\right)\)
\(=-4\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{98}-\frac{1}{99}\right)\)
\(=-4\left(1-\frac{1}{99}\right)=-\frac{392}{99}\)
Tính hợp lí:
\(\dfrac{-4}{1.2}+\dfrac{-4}{2.3}+\dfrac{-4}{3.4}+...+\dfrac{-4}{97.98}+\dfrac{-4}{98.99}\)
Timx:(4/1.3+4/3.5+4/5.7+...+4/97.99)+4x=7/1.2+7/2.3+7/3.4+...+7/98.99
Tính S= 1+1/2+1/4+1/8+1/16+1/32
Tính tổng A=1.2+2.3+3.4+...+98.99
tinh tong A và B biết:A=1.2+2.3+3.4+4.5+5.6+...+98.99;B=1^2+2^2-3^2+4^2+....+98^2
Tính các biểu thức sau:
C=1.2+2.3+3.4+...+98.99
D=(1.99+2.99+3.99+...99.99)-(1.2+2.3+3.4+...98.99
Tính Tổng :
Q= 2+2^2+2^3+2^4+2^5+.......+2^97+2^98+2^99
P=1.2+2.3+3.4+.......+98.99+99.100
B=12/1.2×22/2.3×32/3.4×42/4.5...982/98.99
Tính các biểu thức sau
A=\((1+\frac{1}{1.3})\)\((1+\frac{1}{2.4})\)...\((1+\frac{1}{99.100})\)
B=\((1-\frac{1}{4})\)\((1-\frac{1}{9})\)...\((1-\frac{1}{225})\)
C=1.2+2.3+3.4+...+98.99
D=(1.99+2.99+3.99+...+99.99)-(1.2+2.3+3.4+...+98.99)
Tinh
1) 1^2 + 3^2 + 5^2 + ... + 97^2 + 99^2
2) 1^2 - 2^2 + 3^2 - 4^2 + ... + 99^2 - 100^2
3) 1.2^2 + 2.3^2 + 3.4^2 + ... + 98.99^2
