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B1 Nhân biểu tthức trên với 1/2 được
1/6+1/12/+1/20+....+1/110=1/2×3+1/3×4+.....+1/10×11
=1/2-1/3+1/3-1/4+.....+1/10-1/11=1/2-1/11=9/22
B2
B.1/1×2+1/2×3+.....+1/99×100=1-1/2 +1/2-1/3+....+1/99-1/100=1-1/100=99/100
Phần a sai đề phải llà1/2×4+1/4×6+.....+1/8×10 mới làm đc nhé
= \(x^8.\frac{1}{10}.\frac{2}{9}.\frac{3}{8}.\frac{4}{7}.\frac{5}{6}.\frac{6}{5}.\frac{7}{4}.\frac{8}{3}.\frac{9}{2}\)
= \(x^8.\frac{1}{10}.\left(\frac{2}{9}.\frac{9}{2}\right).\left(\frac{3}{8}.\frac{8}{3}\right).\left(\frac{4}{7}.\frac{7}{4}\right).\left(\frac{5}{6}.\frac{6}{5}\right)\)
= \(x^8.\frac{1}{10}.1.1.1.1\)
= \(x^8.\frac{1}{10}\)
Mk ko pik co dung ko nua
a) \(\frac{11}{15}+\frac{5}{7}+\frac{2}{7}+\frac{4}{15}=\left(\frac{11}{15}+\frac{4}{15}\right)+\left(\frac{5}{7}+\frac{2}{7}\right)\)
\(=2\)
b) \(\frac{5}{9}\times\frac{1}{2}\times\frac{5}{9}\times\frac{6}{4}=\frac{25}{81}\times\frac{3}{4}=\frac{25}{108}\)
c) \(\frac{7}{8}\div\frac{1}{2}+\frac{9}{8}\div\frac{1}{2}=\left(\frac{7}{8}+\frac{9}{8}\right)\div\frac{1}{2}\)
\(=2\div\frac{1}{2}=4\)
d) \(\frac{17}{10}+\frac{1}{2}-\frac{7}{10}=\left(\frac{17}{10}-\frac{7}{10}\right)+\frac{1}{2}\)
\(=1+\frac{1}{2}=\frac{3}{2}\)
a) \(\frac{11}{15}+\frac{5}{7}+\frac{2}{7}+\frac{4}{15}\)
\(=\left(\frac{11}{15}+\frac{4}{15}\right)+\left(\frac{5}{7}+\frac{2}{7}\right)\)
\(=1+1\)
\(=2\)
b) \(\frac{5}{9}.\frac{1}{2}.\frac{5}{9}.\frac{6}{4}\)
\(=\left(\frac{5}{9}\right)^2\left(\frac{1}{2}.\frac{6}{4}\right)\)
\(=\frac{25}{81}.\frac{3}{4}\)
\(=\frac{25}{108}\)
c) \(\frac{7}{8}:\frac{1}{2}+\frac{9}{8}:\frac{1}{2}\)
\(=\frac{7}{8}.2+\frac{9}{8}.2\)
\(=2\left(\frac{7}{8}+\frac{9}{8}\right)\)
\(=2.\frac{16}{8}\)
\(=2.2\)
\(=4\)
d) \(\frac{17}{10}+\frac{1}{2}-\frac{7}{10}\)
\(=\left(\frac{17}{10}-\frac{7}{10}\right)+\frac{1}{2}\)
\(=1+\frac{1}{2}\)
\(=\frac{2}{2}+\frac{1}{2}\)
\(=\frac{3}{2}\)
a) (21x11x2x17x4)/(11x17x21x3)
=(21x11x2x17x4)/(11x17x21x3)
=8/3
b) (5x7x13x2)/(7x2x13x5x5)
=1/5
a,(11/15+4/15)+(5/7+2/7)
=1+1
=2
b,5/9x(1/2+6/4)
=5/9x2
=10/9
c,1/2:(7/8+9/8)
=1/2:2
=1
d,(17/10-7/10)+1/2
=1+1/2
=3/2
7/9 - 3/7 + 2/3 - 4/7
= 7/9 + 2/3 - ( 4/7 + 3/7 )
= 13/9 - 1
= 4/9
8,12 x 6 + 16,24 x 4 - 4,06 x 8
= 8,12 x 6 + 8,12 x 2 x 4 - 8,12 : 2 x 8
= 8,12 x 6 + 8,12 x 8 - 8,12 x 4
= 8,12 x ( 6 + 8 - 4 )
= 8,12 x 10
81,2
Ủng hộ nhé ! Chúc bạn học giỏi !
7/9 - 3/7 + 2/3 - 4/7
= 7/9 + 2/3 - 3/7 - 4/7
= 7/9 + 2/3 - [ 3/7 + 4/7 ]
= 13/9 - 1
= 4/9
8,12 * 6 + 16,24 * 4 - 4,06 * 8
= 8,12 * 6 + 8,12 * 2 * 4 - 4,06 * 2 * 4
= 8,12 * 6 + 8,12 * 8 - 8,12 * 4
= 8,12 * [ 6 + 8 - 4 ]
= 8,12 * 10
= 81,2
CHÚC CÁC BẠN THÀNH CÔNG . Nhớ k cho mình nhiều nhiều nhé !
Ta có: \(1\frac{4}{5}+2\frac{5}{7}+3\frac{4}{5}+4\frac{5}{7}\)
\(=\left(1\frac{4}{5}+3\frac{4}{5}\right)+\left(2\frac{5}{7}+4\frac{5}{7}\right)\)
\(=\left(\frac{9}{5}+\frac{19}{5}\right)+\left(\frac{19}{7}+\frac{33}{7}\right)\)
\(=\frac{28}{5}+\frac{52}{7}=13\frac{1}{35}\)
= ( \(1\frac{4}{5}\)+ \(3\frac{4}{5}\)) + ( \(2\frac{5}{7}\)+ \(4\frac{5}{7}\))
= \(4\frac{4}{5}\) + \(6\frac{5}{7}\)
= \(\frac{24}{5}\) + \(\frac{47}{7}\)
= ...... ( tính nốt nhé )
a. \(1\frac{1}{24}\cdot5\frac{2}{5}\cdot3\frac{7}{9}\cdot2\frac{2}{17}\)
\(=\frac{25}{24}\cdot\frac{27}{5}\cdot\frac{34}{9}\cdot\frac{36}{17}\)
\(=\left(\frac{25}{24}\cdot\frac{27}{5}\right)\cdot\left(\frac{34}{9}\cdot\frac{36}{17}\right)=\frac{5\cdot27}{24}\cdot\frac{2\cdot17\cdot9\cdot4}{9\cdot17}=\frac{5\cdot27}{24}\cdot8\)
\(=\frac{5\cdot27\cdot8}{24}=\frac{5\cdot9\cdot3\cdot8}{24}=\frac{45\cdot24}{24}=45\)
b. \(2\frac{3}{13}\cdot\frac{26}{58}\cdot4\cdot2\frac{15}{24}\cdot\frac{8}{21}\)
\(=\frac{29}{13}\cdot\frac{26}{58}\cdot4\cdot\frac{21}{8}\cdot\frac{8}{21}=\frac{29\cdot13\cdot2}{13\cdot29\cdot2}\cdot4\cdot\frac{21\cdot8}{8\cdot21}=1\cdot4\cdot1\)
\(=4\)