=1+1/3+1/5+..+1/97+1/99
=(1+1/99)+(1/3+1/97)+...+(1/49+1/51)
=100/1.99+100/3.97+......+100/49.50
=100/(1/1.99+1/3.97+......+1/49.50)
=100/(1-1/99+1/3-1/97+.........+1/49-1/50)
=100/(1-1/50)
=100:49/50
=
a=1*3+3*5+5*7+......+97*99+99*101
tinh a
1+1/3+1/5+.....+1/97+1/99
1/1*99+1/3*97+1/5*95+...+1/97*3+1/99*1
tinh nhanh day so 1+2-3+4+5-6....+97+98-99
1/99*97-1/97*95-...-1/5*3-1/3*1
1/99*97-1/97*95-1/95*93-...-1/5*3-1/3*1=
\(\frac{1+\frac{1}{3}+\frac{1}{5}+...+\frac{1}{97}+\frac{1}{99}}{\frac{1}{1\cdot99}+\frac{1}{3\cdot97}+\frac{1}{5\cdot99}+...+\frac{1}{97\cdot3}+\frac{1}{99\cdot1}}\)
Tinh:
A=1+5+5^2+...+5^120
B=3^100-3^99+3^98-3^97+...+3^2-3+1
C=1+7+7^2+...+7^2016
D=2^100-2^99+2^98-2^97+...+2^2-2
giup m voi
thanks
Tính M=1/99*97-1/97*95-1/95*93-...-1/5*3-1/3*1
Tính
A=\(\frac{1+\frac{1}{3}+\frac{1}{5}+...+\frac{1}{97}+\frac{1}{99}}{\frac{1}{1\cdot99}+\frac{1}{3\cdot97}+\frac{1}{5\cdot95}+...+\frac{1}{97\cdot3}+\frac{1}{99\cdot1}}\)
