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\(x^2-7x+1=x^2-6x+9-x+3-11\)
\(=\left(x-3\right)^2-\left(x-3\right)-11\)
\(=\left(x-3\right)\left(x-2\right)-11\)
\(\Rightarrow x^2-7x+1⋮x-3\)
\(\Leftrightarrow\left(x-3\right)\left(x-2\right)-11⋮x-3\Leftrightarrow-11⋮x-3\)
\(\Leftrightarrow x-3\inƯ\left(-11\right)=\left\{1;-1;11;-11\right\}\)
\(\Leftrightarrow x\in\left\{4;2;14;-8\right\}\)
...
Ta có:
\(\left(5x+2\right)⋮\left(7x-1\right)\)
\(\Rightarrow7\left(5x+2\right)⋮\left(7x-1\right)\)
\(\Leftrightarrow\left(35x+14\right)⋮\left(7x-1\right)\)
\(\Leftrightarrow\left[5\left(7x-1\right)+19\right]⋮\left(7x-1\right)\)
\(\Leftrightarrow19⋮\left(7x-1\right)\Leftrightarrow7x-1\inƯ\left(19\right)=\left\{-19;-1;1;19\right\}\)
Mà \(x\in Z\Rightarrow x=0\)(TM)
- Đặt \(f\left(x\right)=x^2-7x+1\) và \(g\left(x\right)=x-3\)
- Ta có: \(f\left(x\right)=\left(x^2-3x\right)-\left(4x-12\right)-11\)
\(\Leftrightarrow f\left(x\right)=x.\left(x-3\right)-4.\left(x-3\right)-11\)
\(\Leftrightarrow f\left(x\right)=\left(x-4\right).\left(x-3\right)-11\)
- Để \(f\left(x\right)⋮g\left(x\right)\)\(\Rightarrow\left(x-4\right).\left(x-3\right)-11⋮x-3\)
mà \(\left(x-4\right).\left(x-3\right)⋮x-3\)\(\Rightarrow11⋮x-3\)\(\Rightarrow x-3\inƯ\left(11\right)\in\left\{\pm1;\pm11\right\}\)
+ \(x-3=1\Leftrightarrow x=4\left(TM\right)\)
+ \(x-3=-1\Leftrightarrow x=2\left(TM\right)\)
+ \(x-3=11\Leftrightarrow x=14\left(TM\right)\)
+ \(x-3=-11\Leftrightarrow x=-8\left(TM\right)\)
Vậy \(x\in\left\{-8;2;4;14\right\}\)
Tạ Đức Hoàng Anh TM là gì vậy bạn