Tính hợp lý A=2/3.5+2/5.7+2/7.9+……….+2/37.39 B=1/2.3+1/3.4+1/4.5+………………………+1/99.100 29/09/2021 Bởi Remi Tính hợp lý A=2/3.5+2/5.7+2/7.9+……….+2/37.39 B=1/2.3+1/3.4+1/4.5+………………………+1/99.100
Đáp án: A = $\frac{8}{13}$ B = $\frac{49}{100}$ Giải thích các bước giải: A = $\frac{2}{3.5}$ + $\frac{2}{5.7}$ + $\frac{2}{7.9}$ + …… + $\frac{2}{37.39}$ A = 2 . ($\frac{1}{3.5}$ + $\frac{1}{5.7}$ + $\frac{1}{7.9}$ + ….. + $\frac{1}{37.39}$ A = 2 . ($\frac{1}{3}$ – $\frac{1}{5}$ + $\frac{1}{5}$ – $\frac{1}{7}$ + $\frac{1}{7}$ – $\frac{1}{9}$ +….+ $\frac{1}{37}$ – $\frac{1}{39}$) A = 2 . ($\frac{1}{3}$ – $\frac{1}{39}$) A = 2 . $\frac{4}{13}$ A = $\frac{8}{13}$ B = $\frac{1}{2.3}$ + $\frac{1}{3.4}$ + $\frac{1}{4.5}$ +…….+ $\frac{1}{99.100}$ B = $\frac{1}{2}$ – $\frac{1}{3}$ + $\frac{1}{3}$ – $\frac{1}{4}$ + $\frac{1}{4}$ – $\frac{1}{5}$ +…..+ $\frac{1}{99}$ – $\frac{1}{100}$ B = $\frac{1}{2}$ – $\frac{1}{100}$ B = $\frac{49}{100}$ (Học tốt =^=. Nhớ cho mik câu trả lời hay nhất nha) Bình luận
A = 2/3.5+2/5.7+2/7.9+……….+2/37.39 = 1/2 ( 2/3.5+2/5.7+2/7.9+……….+2/37.39) = 1/2( 1/3.5+1/5.7+1/7.9+……….+1/37.39) = 1/2 ( 1/3 – 1/5 + 1/5-1/7 + … + 1/37 – 1/39) = 1/2( 1/3 – 1/39) = 1/2 . 4/13 = 2/13 B = 1/2.3+1/3.4+1/4.5+………………………+1/99.100 = 1/2 – 1/3 +1/3 – 1/4 +1/4-1/5 +…+ 1/99 – 1/100 = 1/2 – 1/100 = 49/100 Bình luận
Đáp án:
A = $\frac{8}{13}$
B = $\frac{49}{100}$
Giải thích các bước giải:
A = $\frac{2}{3.5}$ + $\frac{2}{5.7}$ + $\frac{2}{7.9}$ + …… + $\frac{2}{37.39}$
A = 2 . ($\frac{1}{3.5}$ + $\frac{1}{5.7}$ + $\frac{1}{7.9}$ + ….. + $\frac{1}{37.39}$
A = 2 . ($\frac{1}{3}$ – $\frac{1}{5}$ + $\frac{1}{5}$ – $\frac{1}{7}$ + $\frac{1}{7}$ – $\frac{1}{9}$ +….+ $\frac{1}{37}$ – $\frac{1}{39}$)
A = 2 . ($\frac{1}{3}$ – $\frac{1}{39}$)
A = 2 . $\frac{4}{13}$
A = $\frac{8}{13}$
B = $\frac{1}{2.3}$ + $\frac{1}{3.4}$ + $\frac{1}{4.5}$ +…….+ $\frac{1}{99.100}$
B = $\frac{1}{2}$ – $\frac{1}{3}$ + $\frac{1}{3}$ – $\frac{1}{4}$ + $\frac{1}{4}$ – $\frac{1}{5}$ +…..+ $\frac{1}{99}$ – $\frac{1}{100}$
B = $\frac{1}{2}$ – $\frac{1}{100}$
B = $\frac{49}{100}$
(Học tốt =^=. Nhớ cho mik câu trả lời hay nhất nha)
A = 2/3.5+2/5.7+2/7.9+……….+2/37.39
= 1/2 ( 2/3.5+2/5.7+2/7.9+……….+2/37.39)
= 1/2( 1/3.5+1/5.7+1/7.9+……….+1/37.39)
= 1/2 ( 1/3 – 1/5 + 1/5-1/7 + … + 1/37 – 1/39)
= 1/2( 1/3 – 1/39)
= 1/2 . 4/13
= 2/13
B = 1/2.3+1/3.4+1/4.5+………………………+1/99.100
= 1/2 – 1/3 +1/3 – 1/4 +1/4-1/5 +…+ 1/99 – 1/100
= 1/2 – 1/100
= 49/100