TL

a 4/8+8/24=1/2+1/3=5/6

b8/28+5/30=2/7+1/6=19/42

nhé

HT

\(a,\frac{8}{15}+\frac{2}{3}=\frac{8+10}{15}=\frac{18}{15}=\frac{6}{5}\)

\(b,\frac{3}{7}+\frac{4}{8}=\frac{24+28}{56}=\frac{62}{56}=\frac{31}{28}\)

a) \(\frac{8}{15}+\frac{2}{3}=\frac{8}{15}+\frac{10}{15}=\frac{8+10}{15}=\frac{18}{15}=\frac{6}{5}\)

b) \(\frac{3}{7}+\frac{4}{8}=\frac{24}{56}+\frac{28}{56}=\frac{24+28}{56}=\frac{52}{56}=\frac{13}{14}\)

a)2/5+3/5 = 1

b)7/8+5/8 = 12/8= 3/2

c) 1/2+1/3 = 5/6

d) 2/7+1/6= 19/42

a, 2/5 + 9/15          28/32 + 45/72               b, 4/8 + 8/24                 8/28 + 5/30

= 2/5 + 3/5            = 7/8 + 5/8                     = 1/2 + 1/3                   = 2/7 + 1/6

= 1.                        = 3/2.                              = 5/6.                            = 19/42.

k cho mik nha !

1.

a) \(\frac{16}{24}-\frac{1}{3}=\frac{16}{24}-\frac{8}{24}=\)\(\frac{8}{24}=\frac{1}{3}\)

b) \(\frac{4}{5}-\frac{12}{60}=\frac{48}{60}-\frac{12}{60}=\frac{36}{60}=\frac{9}{15}\)

3.

a)\(\frac{17}{6}-\frac{2}{6}=\frac{17-2}{6}=\frac{15}{6}\)

b) \(\frac{16}{15}-\frac{11}{15}=\frac{16-11}{15}=\frac{5}{15}=\frac{1}{3}\)

c) \(\frac{19}{12}-\frac{13}{12}=\frac{19-13}{12}=\frac{6}{12}=\frac{1}{2}\)

\(\frac{1+2^4+2^8+.....+2^{20}}{2^4+2^8+.......+2^{24}}=\frac{1+2^4+2^8+....+2^{20}}{2^4\cdot\left(1+2^4+2^8+...+2^{20}\right)}\)

\(=\frac{1}{2^4}=\frac{1}{16}\)

\(A=\frac{3}{4}.\frac{8}{9}.\frac{15}{16}....\frac{899}{900}\)

\(=\frac{1.3}{2.2}.\frac{2.4}{3.3}.\frac{3.5}{4.4}....\frac{29.31}{30.30}\)

\(=\frac{1.2.3....29}{2.3.4....30}.\frac{3.4.5....31}{2.3.4....30}\)

\(=\frac{1}{30}.\frac{31}{2}=\frac{31}{60}\)

\(A=\frac{1\cdot3}{2\cdot2}\cdot\frac{2\cdot4}{3\cdot3}\cdot...\cdot\frac{29\cdot31}{30\cdot30}\)

\(A=\frac{1\cdot2\cdot...\cdot29}{2\cdot3\cdot...\cdot30}\cdot\frac{3\cdot4\cdot...\cdot31}{2\cdot3\cdot...\cdot30}=\frac{1}{30}\cdot\frac{31}{2}=\frac{31}{60}\)

Ta có : \(A=\frac{3}{4}.\frac{8}{9}.\frac{15}{16}.....\frac{899}{900}\)

          \(A=\frac{3.8.15.....899}{4.9.16.....900}\)

         \(A=\frac{\left(1.3\right).\left(2.4\right).\left(3.5\right).....\left(29.31\right)}{2^2.3^2.4^2.....30^2}\)

        \(A=\frac{\left(1.2.3.....29\right).\left(3.4.5.....31\right)}{\left(2.3.4.....30\right).\left(2.3.4.....30\right)}\)

       \(A=\frac{1.31}{30.2}\)

       \(A=\frac{31}{60}\)

1, Rút gọn rồi tính 

a) \(\frac{4}{5}+\frac{3}{15}\)

= \(\frac{4}{5}+\frac{1}{5}\)

= \(\frac{5}{5}\)

= \(1\)

b) \(\frac{2}{3}+\frac{32}{24}\)

= \(\frac{2}{3}+\frac{4}{3}\)

= \(\frac{6}{3}\)

= \(2\)

c) \(\frac{5}{6}+\frac{15}{18}\)

= \(\frac{5}{6}+\frac{5}{6}\)

= \(\frac{10}{6}\)

= \(\frac{5}{3}\)

2, Tính rồi rút gọn 

a) \(\frac{8}{15}+\frac{2}{3}\)

= \(\frac{8}{15}+\frac{10}{15}\)

= \(\frac{18}{15}\)

= \(\frac{6}{5}\)

b) \(\frac{3}{7}+\frac{4}{8}\)

= \(\frac{24}{56}+\frac{28}{56}\)

= \(\frac{52}{56}\)

= \(\frac{13}{14}\)

Đáp án:

a) 1

b) 2

c) 5/3

Bài 3.Tính rồi rút gọn

a)6/5

b) 13/14

a) 4/5+3/15=4/5+1/5=1

b) 2/3+32/24=2/3+4/3=2

c)5/6+15/18=5/6+5/6=5/3

3.

a)8/15+2/3=18/15=6/5

b)3/7+4/8=52/56=13/14

Nhớ k cho mình đó !

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