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= \(\frac{9}{1x4}+\frac{9}{4x7}+\frac{9}{7x10}+.........+\frac{9}{19x22}+\frac{9}{22x25}\)
= \(\frac{1}{3}x\left(\frac{9}{1}-\frac{9}{4}\right)+\left(\frac{9}{4}-\frac{9}{7}\right)x\frac{1}{3}+........+\left(\frac{9}{22}-\frac{9}{25}\right)x\frac{1}{3}\)
= \(\frac{1}{3}\left(\frac{9}{1}-\frac{9}{4}+\frac{9}{4}-\frac{9}{7}+....+\frac{9}{22}-\frac{9}{25}\right)\)
= \(\frac{1}{3}x\left(\frac{9}{1}-\frac{9}{25}\right)\)
= \(\frac{1}{3}x\frac{216}{25}\)
= \(\frac{72}{25}\)
nhớ ********** nha bn thân
\(\frac{9}{4}+\frac{9}{28}+\frac{9}{70}+\frac{9}{130}+...+\frac{9}{418}+\frac{9}{550}\)
\(=3\left(\frac{3}{1.4}+\frac{3}{4.7}+...+\frac{3}{19.22}+\frac{3}{22.25}\right)\)
\(=3\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+...+\frac{1}{22}-\frac{1}{25}\right)\)
\(=3\left(1-\frac{1}{25}\right)\)
\(=3.\frac{24}{25}=\frac{72}{25}\)
\(\dfrac{4}{3}\times3+\dfrac{2}{5}=4+\dfrac{2}{5}=\dfrac{22}{5}\)
a) S
b) Đ
c) Đ
d) S
Nếu đúng thì Kết bạn rồi k đúng cho mình nhé ;)
a.5 / 24 x 5 / 12 x 24 = 600 / 288
b.(1 / 4 + 2 / 3)x 4 / 5 = 44/60
a. 5/24 x 5/12 x24 = 600/288 = 25/12 ( rút gọn,tối giản)
b.(1/4 + 2/3) x 4/5 = 1/6 x 4/5 = 4/30 = 2/15 ( rút gọn,tối giản)
c. 3/7 x 16/33 + 16/33 x 4/7 = 16/33 x ( 3/7+4/7) = 16/33 x 7/7=16/33 x 1 = 16/33
CÔNG THỨC = TỬ NHÂN TỬ, MẪU NHÂN MẪU ( RÚT GỌN,TỐI GIẢN NẾU CÓ THỂ)
#HOC_TOT_NHA ><
đúng thì k mk nha
Ta có:
\(\frac{3}{4}+\frac{3}{28}+\frac{3}{70}+\frac{3}{130}+\frac{3}{208}\)
\(=\frac{3}{1\times4}+\frac{3}{4\times7}+\frac{3}{7\times10}+\frac{3}{10\times13}+\frac{3}{13\times16}\)
\(=\frac{4-1}{1\times4}+\frac{7-4}{4\times7}+\frac{10-7}{7\times10}+\frac{13-10}{10\times13}+\frac{16-13}{13\times16}\) \(=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+\frac{1}{13}-\frac{1}{16}\)
\(=1-\frac{1}{16}\)
\(=\frac{15}{16}\)
Chắc chắn đúng nhé !
vế 1 (6:4 =1.5 )x(19:10 =1.9)1,5x1,9 =2,85
vế 2 (3/4=0,75)x(7:10=0,7)0,75x0,7=0,525
vế 3 (3:4=0,75):(10:69=0,14492753623 lấy 3 chữ số ở hàng thập phân =0,144) 0,75:0,144=6,57894736842 lấy 3 chữ số ở hàng thập phân =6,578
2,85 -0,525+6,578
=2,325+6,578
=8.903
(hơi rườm rà nếu có sai thông cảm)
vế 1 6/4 x 19/10=57/20
vế 2 3/4 x 7/10=21/40
vế 3 3/4 : 10/69 =207/40
57/20 - 21/40 + 207/40
= 93/40 + 207/40
=15/2
\(C=\dfrac{4}{4}+\dfrac{4}{28}+\dfrac{4}{70}+\dfrac{4}{130}+...+\dfrac{4}{418}+\dfrac{4}{550}\\ =\dfrac{4}{1\times4}+\dfrac{4}{4\times7}+\dfrac{4}{7\times10}+\dfrac{4}{10\times13}+...+\dfrac{4}{19\times22}+\dfrac{4}{22\times25}\\ =\dfrac{4}{3}\times\left(\dfrac{1}{1}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{13}+...+\dfrac{1}{19}-\dfrac{1}{22}+\dfrac{1}{22}-\dfrac{1}{25}\right)\\ =\dfrac{4}{3}\times\left(1-\dfrac{1}{25}\right)=\dfrac{4}{3}\times\dfrac{24}{25}=\dfrac{32}{25}\)
C = \(\dfrac{4}{4}\) + \(\dfrac{4}{28}\)+ \(\dfrac{4}{70}\) + \(\dfrac{4}{130}\)+.....+\(\dfrac{4}{418}\)+ \(\dfrac{4}{550}\)
C = \(\dfrac{4}{3}\)( \(\dfrac{3}{4}\)+\(\dfrac{3}{28}\)+ \(\dfrac{3}{70}\)+ \(\dfrac{3}{130}\)+.....+\(\dfrac{3}{418}\)+ \(\dfrac{3}{550}\))
C = \(\dfrac{4}{3}\)( \(\dfrac{3}{1.4}\)+ \(\dfrac{3}{4.7}\)+ \(\dfrac{3}{7.10}\)+......+\(\dfrac{3}{19.22}\)+\(\dfrac{3}{22.25}\))
C = \(\dfrac{4}{3}\)( \(\dfrac{1}{1}\)- \(\dfrac{1}{4}\)+ \(\dfrac{1}{4}\)- \(\dfrac{1}{7}\)+ \(\dfrac{1}{7}\)- \(\dfrac{1}{10}\)+ ......+\(\dfrac{1}{19}\)- \(\dfrac{1}{22}\)+ \(\dfrac{1}{22}\)- \(\dfrac{1}{25}\))
C = \(\dfrac{4}{3}\)(1- \(\dfrac{1}{25}\))
C = \(\dfrac{4}{3}\) . \(\dfrac{24}{25}\)
C =\(\dfrac{32}{25}\)