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

a) \(\dfrac{x}{12}=\dfrac{6}{9}\)

\(\Rightarrow x=\dfrac{12\cdot6}{9}=8\)

b) \(\dfrac{9}{15}=x+\dfrac{11}{35}\)

\(\Rightarrow x=\dfrac{9}{15}-\dfrac{11}{35}\)

\(\Rightarrow x=\dfrac{2}{7}\)

c) \(x+\dfrac{6}{5}=\dfrac{x}{2}\)

\(\Rightarrow2\left(x+\dfrac{6}{5}\right)=x\)

\(\Rightarrow2x+\dfrac{12}{5}=x\)

\(\Rightarrow2x-x=-\dfrac{12}{5}\)

\(\Rightarrow x=-\dfrac{12}{5}\)

\(a,\dfrac{x}{12}=\dfrac{6}{9}\\ \Leftrightarrow x=12\cdot\dfrac{6}{9}\\ \Leftrightarrow x=8\\ b,\dfrac{9}{15}=x+\dfrac{11}{35}\\ \Leftrightarrow x=\dfrac{9}{15}-\dfrac{11}{35}\\ \Leftrightarrow x=\dfrac{2}{7}\\ c,x+\dfrac{6}{5}=\dfrac{x}{2}\\ \Leftrightarrow\dfrac{x}{2}=-\dfrac{6}{5}\\ \Leftrightarrow x=-\dfrac{12}{5}\)

\(4^5\cdot2^3\)

\(=\left(2^2\right)^5\cdot2^3\)

\(=2^{10}\cdot2^3\)

\(=2^{13}\)

\(4^5\cdot2^3\\ =2^{10}\cdot2^3\\ =2^{10+3}\\ =2^{13}\)

1. a) 40

    b) 3

    c) 18

    d) 3

2. a) 291

    b) 37

    c) 61

    d) 284

\(\left(x-\dfrac{7}{18}\right)\cdot\dfrac{15}{27}=\dfrac{10}{27}\\ \Leftrightarrow x-\dfrac{7}{18}=\dfrac{2}{3}\\ \Leftrightarrow x=\dfrac{19}{18}\)

=10/27