Question

[ẩn nguyễn]

Giúp 2 câu này với ạ : 3x - 5y = 7 ;

( x-3 ) ^ 8 = ( 3x - 9 ) ^ 10

Answer 1

[Nguyễn Lê Phước Thịnh]

\(\left(x-3\right)^8=\left(3x-9\right)^{10}\)

=>\(3^{10}\left(x-3\right)^{10}-\left(x-3\right)^8=0\)

=>\(\left(x-3\right)^8\cdot\left[3^{10}\left(x-3\right)^2-1\right]=0\)

=>\(\left[{}\begin{matrix}x-3=0\\3^5\left(x-3\right)=1\\3^5\left(x-3\right)=-1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=3\\x-3=\dfrac{1}{243}\\x-3=-\dfrac{1}{243}\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}x=3\\x=3+\dfrac{1}{243}=\dfrac{730}{243}\\x=3-\dfrac{1}{243}=\dfrac{729}{243}-\dfrac{1}{243}=\dfrac{728}{243}\end{matrix}\right.\)

TH1: x=3

3x-5y=7

=>5y=3x-7=9-7=2

=>\(y=\dfrac{2}{5}\)

TH2: \(x=\dfrac{730}{243}\)

3x-5y=7

=>5y=3x-7

=>\(5y=3\cdot\dfrac{730}{243}-7=\dfrac{163}{81}\)

=>\(y=\dfrac{163}{405}\)

TH3: \(x=\dfrac{728}{243}\)

3x-5y=7

=>5y=3x-7

=>\(5y=3\cdot\dfrac{728}{243}-7=\dfrac{161}{81}\)

=>\(y=\dfrac{161}{81}:5=\dfrac{161}{405}\)

Answer 2

[Sáng]

1=3/5,2=730/243