Tính B = $\frac{1}{1 .2}$ + $\frac{1}{2.3}$ + $\frac{1}{3.4}$ + . . . + $\frac{1}{2009.2010}$
Tính B = $\frac{1}{1 .2}$ + $\frac{1}{2.3}$ + $\frac{1}{3.4}$ + . . . + $\frac{1}{2009.2010}$
By Ayla
By Ayla
Tính B = $\frac{1}{1 .2}$ + $\frac{1}{2.3}$ + $\frac{1}{3.4}$ + . . . + $\frac{1}{2009.2010}$
Đáp án:
`2009/2010`
Giải thích các bước giải:
B=`1/(1.2)`+ `1/(2.3)`+ `1/(3.4)`+ …… +`1/(2009,2010)`
B= `(2-1)/(1.2)`+ `(3-2)/(2.3)`+ `(4-3)/(3.4)`+ …… +`(2010-2009)/(2009,2010)`
B= 1 -`1/2`+`1/2`-`1/3`+`1/3`-`1/4`+ ………… +`1/2009` – `1/2010`
B = 1 – `1/2010`
B=`2009/2010`
`B = 1/(1.2)+1/(2+3)+1/(3+4)+…+1/(2009+2010)`
`B = 1 – 1/2 + 1/2 -1/3+1/3-1/4+…+1/2009-1/2010`
`B = 1 – 1/2010`
`B = 2009/2010`