Toán B2 TÍNH NHANH 1/3+1/3^2 + 1/3^3 1/3^4 +….+1/3 ^2007 +1/3^2008 09/10/2021 By Julia B2 TÍNH NHANH 1/3+1/3^2 + 1/3^3 1/3^4 +….+1/3 ^2007 +1/3^2008
`A = 1/3+1/3^2 + 1/3^3 +….+1/3^2007 +1/3^2008` `3A = 1 + 1/3+1/3^2 + +….+1/3^2006 +1/3 ^2007` `3A – A = (1 + 1/3+1/3^2 + +….+1/3^2006 +1/3 ^2007) – (1/3+1/3^2 + 1/3^3 +….+1/3^2007 +1/3^2008)` `2A = 1 – 1/3^2008` `A = (1 – 1/3^2008)/2` (Chúc bạn học tốt) Trả lời
đặt A=1/3+1/3^2 + 1/3^3 1/3^4 +….+1/3 ^2007 +1/3^2008 ⇒3A=1+1/3+1/3^2+1/3^3+…+1/3^2006+1/3^2007 ⇒3A-A=(1+1/3+1/3^2+1/3^3+…+1/3^2006+1/3^2007)-(1/3+1/3^2 + 1/3^3 1/3^4 +….+1/3 ^2007 +1/3^2008) ⇒2A=1-1/3^2008 A=(1-1/3^2008)/2 xin hay nhất Trả lời
`A = 1/3+1/3^2 + 1/3^3 +….+1/3^2007 +1/3^2008`
`3A = 1 + 1/3+1/3^2 + +….+1/3^2006 +1/3 ^2007`
`3A – A = (1 + 1/3+1/3^2 + +….+1/3^2006 +1/3 ^2007) – (1/3+1/3^2 + 1/3^3 +….+1/3^2007 +1/3^2008)`
`2A = 1 – 1/3^2008`
`A = (1 – 1/3^2008)/2`
(Chúc bạn học tốt)
đặt A=1/3+1/3^2 + 1/3^3 1/3^4 +….+1/3 ^2007 +1/3^2008
⇒3A=1+1/3+1/3^2+1/3^3+…+1/3^2006+1/3^2007
⇒3A-A=(1+1/3+1/3^2+1/3^3+…+1/3^2006+1/3^2007)-(1/3+1/3^2 + 1/3^3 1/3^4 +….+1/3 ^2007 +1/3^2008)
⇒2A=1-1/3^2008
A=(1-1/3^2008)/2
xin hay nhất