Đặt f(x)=0
nên 3x-6=0
hay x=2
Đặt h(x)=0
nên 30-5x=0
hay x=6
Đặt g(x)=0
\(\Leftrightarrow\left(x-3\right)\left(x-4\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=4\end{matrix}\right.\)
Ta có:
\(f\left(x\right)=0\Leftrightarrow3x-6=0\Leftrightarrow x=2\)
Vậy nghiệm của đa thức f(x) là 2
\(h\left(x\right)=0\Leftrightarrow-5x+30=0\Leftrightarrow x=6\)
Vậy nghiệm của đa thức h(x) là 6
Đặt \(f\left(x\right)=3x-6=0\Leftrightarrow x=2\)
Đặt \(h\left(x\right)=-5x+30=0\Leftrightarrow x=6\)
Đặt \(g\left(x\right)=\left(x-3\right)\left(16-4x\right)=0\Leftrightarrow x=3;x=4\)
Đặt \(k\left(x\right)=x^2-8=0\Leftrightarrow x^2=8\Leftrightarrow x=\pm2\sqrt{2}\)
Đặt \(m\left(x\right)=x^2+7x-8=0\Leftrightarrow\left(x-1\right)\left(x+8\right)=0\Leftrightarrow x=-8;x=1\)
Đặt \(n\left(x\right)=5x^2+9x+4=0\Leftrightarrow\left(5x+4\right)\left(x+1\right)=0\Leftrightarrow x=-\dfrac{4}{5};x=-1\)
\(k\left(x\right)=0\Leftrightarrow x^2-8=0\Leftrightarrow\left[{}\begin{matrix}x=\sqrt{8}\\x=-\sqrt{8}\end{matrix}\right.\)
Vậy....
\(m\left(x\right)=x^2+7x-8=0\Leftrightarrow x^2-x+8x-8=0\Leftrightarrow x\left(x-1\right)+8\left(x-1\right)=0\Leftrightarrow\left(x+8\right)\left(x-1\right)=0\Leftrightarrow\left[{}\begin{matrix}x=-8\\x=1\end{matrix}\right.\)
Vậy...
1) \(f\left(x\right)=3x-6=0\Rightarrow x=2\)
2) \(h\left(x\right)=-5x+30=0\Rightarrow x=6\)
3) \(g\left(x\right)=\left(x-3\right)\left(16-4x\right)=0\)
\(\Rightarrow4\left(x-3\right)\left(4-x\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=3\\x=4\end{matrix}\right.\)
4) \(k\left(x\right)=x^2-8=0\Rightarrow x^2=8\Rightarrow x=\pm\sqrt{8}=\pm2\sqrt{2}\)
5) \(m\left(x\right)=x^2+7x-8=0\)
\(\Rightarrow\left(x-1\right)\left(x+8\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=1\\x=-8\end{matrix}\right.\)
6) \(n\left(x\right)=5x^2+9x+4=0\)
\(\Rightarrow\left(5x+4\right)\left(x+1\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=-\dfrac{4}{5}\\x=-1\end{matrix}\right.\)
