a) \(x^3-16x=0\)
\(\Leftrightarrow x\left(x^2-16\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x=0\\x^2-16=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=0\\x=\pm4\end{cases}}\)
Vậy tập nghiệm \(S=\left\{-4;0;4\right\}\)
b) \(x^4-2x^3+10x^2-20x=0\)
\(\Leftrightarrow x^3\left(x-2\right)+10x\left(x-2\right)=0\)
\(\Leftrightarrow\left(x^3+10x\right)\left(x-2\right)=0\)
\(\Leftrightarrow x\left(x^2+10\right)\left(x-2\right)=0\)
Mà \(x^2+10>0\)nên \(\orbr{\begin{cases}x=0\\x-2=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=0\\x=2\end{cases}}\)
Vậy tập nghiệm S = { 0;2}
c) \(\left(2x-3\right)^2=\left(x+5\right)^2\)
\(\Leftrightarrow\orbr{\begin{cases}2x-3=x+5\\2x-3=-x-5\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=8\\x=\frac{-2}{3}\end{cases}}\)
Vậy tập nghiệm \(S=\left\{\frac{-2}{3};8\right\}\)
bài 1 :
b) \(x^4-3x^3-x+3\)
\(\Rightarrow\)(x\(^4\)-x)+(\(-3x^3+3\))
\(\Rightarrow\) x(\(x^3-1\))+3(\(x^3-1\))
\(\Rightarrow\)(\(x^3-1\))(x+3)
b) \(x^4-3x^3-x+3\)
\(=x^3\left(x-3\right)-\left(x-3\right)\)
\(=\left(x^3-1\right)\left(x-3\right)\)
\(=\left(x-1\right)\left(x^2+x+1\right)\left(x-3\right)\)
\(d,3x+3y-x^2-2xy-y^2\)
\(=3\left(x+y\right)-\left(x^2+2xy+y^2\right)\)
\(=3\left(x+y\right)-\left(x+y\right)^2\)
\(=\left(x+y\right)\left(3-x-y\right)\)
bài 2 c
\(\left(2x-3\right)^2\)=\(\left(x+5\right)^2\)
\(\Rightarrow\)\(\left(2x-3\right)^2-\left(x+5\right)^2\)=0
\(\Rightarrow\)\(\left(2x-3-x-5\right)\)\(\left(2x-3+x+5\right)\)=0
\(\Rightarrow\) \(\orbr{\begin{cases}2x-3-x-5=0\\2x-3+x+5=0\end{cases}}\)\(\Leftrightarrow\)\(\orbr{\begin{cases}x=8\\x=-2\end{cases}}\)
vậy S={8,-2}