a,x.(3\4+2\5)=1

x.20\23=1

x=1:20\23

x=20\23

b,x-9\11=0 hoặc x-25\31=0

x=9\11                x=25\31

c,x-3\7.9\14=7\3

x-2\3=7\3

x=7\3+2\3

x=9\3

x=3

a, \(\dfrac{1}{2}\) - ( - \(\dfrac{1}{3}\) ) + \(\dfrac{1}{23}\) + \(\dfrac{1}{6}\)

 =  \(\dfrac{5}{6}\)  + \(\dfrac{1}{23}\) + \(\dfrac{1}{6}\)

= 1 + \(\dfrac{1}{23}\)

 = \(\dfrac{24}{23}\) 

b, \(\dfrac{11}{24}\) - \(\dfrac{5}{41}\) + \(\dfrac{13}{24}\) + 0,5 - \(\dfrac{36}{41}\)

= (\(\dfrac{11}{24}\) + \(\dfrac{13}{24}\)) - ( \(\dfrac{5}{41}\) + \(\dfrac{36}{41}\)) + 0,5

= 1 - 1 + 0,5

= 0,5 

c,\(-\dfrac{1}{12}-\left(\dfrac{1}{6}-\dfrac{1}{4}\right)\)

=\(-\dfrac{1}{12}-\left(-\dfrac{1}{12}\right)\)

=0

d, \(\dfrac{1}{6}-\left[\dfrac{1}{6}-\left(\dfrac{1}{4}+\dfrac{9}{12}\right)\right]\)

= \(\dfrac{1}{6}-\left[\dfrac{1}{6}-1\right]\)

= \(\dfrac{1}{6}-\left(-\dfrac{5}{6}\right)\)

= 1

Rút gọn: \(\dfrac{28}{-6}=\dfrac{14}{3}\)

Quy đồng: \(-5=-\dfrac{15}{3}\)

Vì \(14>-15\) nên \(\dfrac{28}{-6}>-5\)

\(\dfrac{28}{6}=\dfrac{30-2}{6}=5-\dfrac{2}{6}=5-\dfrac{1}{3}< 5\)

\(\Rightarrow\dfrac{28}{6}< 5\Rightarrow-\dfrac{28}{6}>-5\Rightarrow\dfrac{28}{-6}>-5\)

275 = 5².11

380 = 2².5.19

780 = 2².3.5.13

2028 = 2².3.13²

3600 = 2⁴.3².5²

460 = 2².5.23

1410 = 2.3.5.47

2605 = 5.521

3420 = 2².3².5.19

720 = 2⁴.3².5

246 = 2.3.41

a) \(\left(x+4\right).\left(y-1\right)=13\)

\(x+4=13\) hoặc \(y-1=13\)

\(x=13-4\) hoặc \(y=13+1\)

Vậy \(x=9;y=14\)

b) \(xy-3x+y=20\)

\(x\left(y-3\right)+y+3=20+3\)

\(x\left(y-3\right)+\left(y-3\right)=23\)

\(\left(y-3\right).\left(x+1\right)=23\)

\(y-3=23\) hoặc \(x+1=23\)

\(y=23+3\) hoặc \(x=23-1\)

Vậy \(y=26;x=22\)

tick cho mink nhé ✔

\(C=1+5^2+5^3+5^4+...+5^{200}\)

\(\Rightarrow C+5=1+5+5^2+5^3+5^4+...+5^{200}\)

\(\Rightarrow C+5=\dfrac{5^{200+1}-1}{5-1}\)

\(\Rightarrow C+5=\dfrac{5^{201}-1}{4}\)

\(\Rightarrow C=\dfrac{5^{201}-1}{4}-5\)

\(\Rightarrow C=\dfrac{5^{201}-21}{4}\)

a) \(\dfrac{3}{8}+\dfrac{15}{-25}+\dfrac{3}{5}\)

\(=\dfrac{-9}{40}+\dfrac{3}{5}\)

\(=\dfrac{3}{8}\)

b) \(\dfrac{-5}{18}+\dfrac{23}{45}-\dfrac{9}{10}\)

\(=\dfrac{7}{30}-\dfrac{9}{10}\)

\(=\dfrac{-2}{3}\)

c) \(\dfrac{-5}{12}+\dfrac{15}{18}-2,25\)

\(=\dfrac{5}{12}-2,25\)

\(=\dfrac{-11}{6}\)

d) \(\dfrac{5}{6}+\dfrac{2}{3}-0,5\)

\(=\dfrac{3}{2}-0,5\)

\(=1\)

tick cho mink nhé bn ✔

a: Số phần học sinh của đoàn đã đến là

\(\dfrac{3}{5}.\dfrac{3}{4}=\dfrac{9}{20}\)

b: Số bạn nam đén điểm tập trung rồi là 60*9/20=27 bạn

Số bạn chưa đến tập trung là:

60-27=33 bạn

a) 9/20

b) 27

c) 33