Tính nhanh:
A = [1 + 1/5] * [1 + 1/24] * [1 + 1/35] * ... * [1 + 1/9999]
Tính nhanh:A=1/15+1/35+1/63+1/99+...+1/9999
A = 1/15 + 1/35 + 1/63 + 1/99 +........1/9999
A = 1/3x5 + 1/5x7 + 1/7x9 + .......+ 1/99x101
A = 1/2 x (1/3 - 1/5 + 1/5 - 1/7 + 1/7 - 1/9 +..... + 1/99 - 1/101)
A = 1/2 X ( 1/3 - 1/99)
A = 1/2 x ( 1/3 - 1/101)
A = 1/2 ( 98/303)
A = 49/303
tính nhanh:a=1/15+1/35+1/63+1/99+.....+1/9999
a bằng bao nhiêu?
A = 1/15 + 1/35 + 1/ 63 + 1/99 + ...+ 1/9999
A = 1/(3x5) + 1/(5x7) + 1/(7x9) + 1/(9x11) + ... + 1/(99 x 101)
Ax2 = 2/(3x5) + 2/(5x7) + 2/(7x9) + 2/(9x11) + ... + 2/(99 x 101)
Ax2 = 1/3 – 1/5 + 1/5 – 1/7 + 1/7 – 1/9 + 1/9 – 1/11 + ...+ 1/99 – 1/101
Ax2 = 1/3 – 1/101 = 98/303
A = 98/303 : 2
A = 49/303
tớ không chắc nhé
B=(1+1/15)*(1+1/24)*(1+1/35)*...*(1+1/9999)
B = 16/15 . 25/24 . ....... . 10000/9999
= 4.4/3.5 . 5.5/4.6 . ...... . 100.100/99.101
= 4.5. ..... .100/3.4. .... .99 . 4.5. ..... .100/5.6. ..... .101
= 100/3 . 4/101
= 400/303
Tk mk nha
Tính nhanh:A=1/4+1/12+1/24+1/24+1/40+1/60+1/84
2A=1/2+1/6+1/12+1/20+1/30+1/42
=1/1.2+1/2.3+1/3.4+1/4.5+1/5.6+1/6.7
=1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=1-1/7
=6/7
a=1/5+1/15+1/35..........+1/9999
a=1/5+1/15+1/35+.........+1/9999
Tính
A=1/5+1/35+1/63+1/99+....+1/9999
\(\Rightarrow A=\frac{1}{2}.\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{99}-\frac{1}{101}\right)+\frac{1}{5}\)
\(\Rightarrow A=\frac{1}{2}.\left(\frac{1}{5}-101\right)-\frac{1}{5}=\frac{48}{505}-\frac{1}{5}=-\frac{53}{505}\)
SOS
Giúp tui với
Tính+nhanh:A=1/8+1/24+1/48+1/80
A=1+18+124+148+180+1120A=1+18+124+148+180+1120
=1+12.4+14.6+16.8+18.10+110.12=1+12.4+14.6+16.8+18.10+110.12
=1+12(12−14+14−16+16−18+18−110+110−112)=1+12(12−14+14−16+16−18+18−110+110−112)
=1+12(12−112)=1+12(12−112)
=1+524=1+524
=2924
Tham khảo thôi nka
2A= 2/8+2/24+2/48+2/80= 2/(2*4)+2/(4*6)+2/(6*8)+2/(8*10)= 1/2-1/4+1/4-1/6+1/6-1/8+1/8-1/10= 1/2-1/10= 2/5 =>A= 1/5
\(A=\dfrac{1}{8}+\dfrac{1}{24}+\dfrac{1}{48}+\dfrac{1}{80}=\dfrac{1}{2\times4}+\dfrac{1}{4\times6}+\dfrac{1}{6\times8}+\dfrac{1}{8\times10}\)
\(2A=\dfrac{2}{2\times4}+\dfrac{2}{4\times6}+\dfrac{2}{6\times8}+\dfrac{2}{8\times10}\\ 2A=\dfrac{2}{2}-\dfrac{2}{4}+\dfrac{2}{4}-\dfrac{2}{6}+\dfrac{2}{6}-\dfrac{2}{8}+\dfrac{2}{8}-\dfrac{2}{10}\\ 2A=\dfrac{2}{2}-\dfrac{2}{10}=\dfrac{4}{5}\\ A=\dfrac{2}{5}\)
tính nhanh:1 1/8 x 1 /15 x 1 /24 x 1 1/35 x ........... 1 1/9999 khó lắm đó nha nếu biết cách giải thì viết ra rồi gửi cho mình nha