7⁷⁶⁵⁴=(7²)³⁸²⁷=49³⁸²⁷

2²⁶⁷⁸⁹=(2⁷)³⁸²⁷=128³⁸²⁷

vi 49³⁸²⁷<128³⁸²⁷

vay 7⁷⁵⁶⁴<2²⁶⁷⁸⁹

\(A=\frac{1-2x}{x+1}=\frac{-2\left(x+1\right)+3}{x+1}=-2+\frac{3}{x+1}\)

Để : \(A\inℤ\Leftrightarrow-2+\frac{1}{x+1}\inℤ\Leftrightarrow\frac{1}{x+1}\inℤ\)

\(\Leftrightarrow1⋮x+1\) hay \(x+1\inƯ\left(1\right)=\left\{-1,1\right\}\)

\(\Rightarrow x\in\left\{-2,0\right\}\)

Vậy : \(x\in\left\{-2,0\right\}\)

Nick bạn thì có cái cc gì mà phải mua :))

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\(A=\frac{1+2018.2019}{2017.2019+2020}=\frac{1+2019+2017.2019}{2017.2019+2020}=\frac{2020+2017.2019}{2017.2019+2020}=1\)

\(xy-y^2-2x+4y=0\)

\(\Leftrightarrow y\left(x-y\right)-2\left(x-y\right)+2y=0\)

\(\Leftrightarrow\left(x-y\right)\left(y-2\right)+2y=0\)

Khai triển tiếp ....

Đắt!!!!!!!!!!!!!!!! kinh!

a) \(\frac{-7}{15}.\frac{5}{8}.\frac{15}{-7}.\left(-16\right)\)

\(=\left(\frac{-7}{15}.\frac{15}{-7}\right).\left[\frac{15}{8}.\left(-16\right)\right]\)

\(=1.\left[15.\left(-2\right)\right]=1.\left(-30\right)=-30\)

b) \(\left(-\frac{1}{2}\right).3\frac{1}{5}+\left(-\frac{1}{2}\right).\left(-2\frac{1}{5}\right)\)

\(=\left(-\frac{1}{2}\right).\left(3\frac{1}{5}-2\frac{1}{5}\right)\)

\(=\left(-\frac{1}{2}\right).1=-\frac{1}{2}\)