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HL
0
TC
5 tháng 1 2018
\(x^3-9x^2+6x+16\)
\(=\left(x^3+x^2\right)-\left(10x^2+10x\right)+\left(16x+16\right)\)
\(=x^2\left(x+1\right)-10x\left(x+1\right)+16\left(x+1\right)\)
\(=\left(x+1\right)\left(x^2-10x+16\right)\)
\(=\left(x+1\right)\left[\left(x^2-2x\right)-\left(8x-16\right)\right]\)
\(=\left(x+1\right)\left(x-2\right)\left(x-8\right)\)
HN
5 tháng 8 2016
\(x^3-4x^2-8x+8\)
\(\Leftrightarrow\left(x^3-4x^2\right)-\left(8x-8\right)\)
\(\Leftrightarrow x^2\left(x-4\right)-4\left(x-4\right)\)
\(\Leftrightarrow\left(x-4\right)\left(x^2-4\right)\)
VV
1
HP
7 tháng 8 2018
1) \(x^3+5x^2+9x=-45\)
\(\Rightarrow x^2\left(x+5\right)+9x+45=0\)
\(\Rightarrow x^2\left(x+5\right)+9\left(x+5\right)=0\)
\(\Rightarrow\left(x^2+9\right)\left(x+5\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x^2+9=0\\x+5=0\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x^2=-9\left(loai\right)\\x=-5\left(nhan\right)\end{cases}}\)
2) \(x^3-6x^2-x+30=0\)
\(\Rightarrow x^3-3x^2-3x^2+9x-10x+30=0\)
\(\Rightarrow x^2\left(x-3\right)-3x\left(x-3\right)-10\left(x-3\right)=0\)
\(\Rightarrow\left(x^2-3x-10\right)\left(x-3\right)=0\)
\(\Rightarrow\left(x^2-5x+2x-10\right)\left(x-3\right)=0\)
\(\Rightarrow\left[x\left(x-5\right)+2\left(x-5\right)\right]\left(x-3\right)=0\)
\(\Rightarrow\left(x+2\right)\left(x-3\right)\left(x-5\right)=0\)
\(\)Từ đây giải x giống câu trên nhé.
3) \(x^2+16=10x\)
\(\Rightarrow x^2-10x+16=0\)
\(\Rightarrow\left(x-8\right)\left(x-2\right)=0\)
Tương tự....
28 tháng 7 2017
Ta có: \(x^3-9x^2+6x+16\)
\(=x^3-2x^2-7x^2+14x-8x+16\)
\(=x^2\left(x-2\right)-7x\left(x-2\right)-8\left(x-2\right)\)
\(=\left(x-2\right)\left(x^2-7x-8\right)\)
\(=\left(x-2\right)\left(x^2-8x+x-8\right)\)
\(=\left(x-2\right)\left[x\left(x-8\right)+\left(x-8\right)\right]\)
\(=\left(x-2\right)\left(x-8\right)\left(x+1\right)\)
k cho mình nha bn thanks nhìu <3
HB
2
CW
26 tháng 7 2017
a) bt \(=\left(x-8\right)\left(x^2-x-2\right)=\left(x-8\right)\left(x+1\right)\left(x-2\right)\)
kl: ...
b) \(=\left(x+2\right)\left(x^2-8x-15\right)=\left(x+2\right)\left(x-5\right)\left(x-3\right)\)
kl:....
DH
26 tháng 7 2017
a, \(x^3-9x^2+6x+16\)
\(=x^3-8x^2-x^2+8x-2x+16\)
\(=x^2\left(x-8\right)-x\left(x-8\right)-2\left(x-8\right)\)
\(=\left(x-8\right)\left(x^2-x-2\right)\)
\(=\left(x-8\right)\left(x^2-2x+x-2\right)\)
\(=\left(x-8\right)\left[x\left(x-2\right)+\left(x-2\right)\right]\)
\(=\left(x-8\right)\left(x-2\right)\left(x+1\right)\)
b, \(x^3-6x^2-x+30\)
\(=x^3-5x^2-x^2+5x-6x+30\)
\(=x^2\left(x-5\right)-x\left(x-5\right)-6\left(x-5\right)\)
\(=\left(x-5\right)\left(x^2-x-6\right)\)
\(=\left(x-5\right)\left(x^2-3x+2x-6\right)\)
\(=\left(x-5\right)\left[x\left(x-3\right)+2\left(x-3\right)\right]\)
\(=\left(x-5\right)\left(x-3\right)\left(x+2\right)\)
Chúc bạn học tốt!!!
14 tháng 9 2020
a) Ta có: \(x^4-16x^2=0\)
\(\Leftrightarrow x^2\left(x^2-16\right)=0\)
\(\Leftrightarrow x^2\left(x-4\right)\left(x+4\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x^2=0\\x-4=0\\x+4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=4\\x=-4\end{matrix}\right.\)
Vậy: \(x\in\left\{0;4;-4\right\}\)
b) Ta có: \(9x^2+6x+1=0\)
\(\Leftrightarrow\left(3x\right)^2+2\cdot3x\cdot1+1^2=0\)
\(\Leftrightarrow\left(3x+1\right)^2=0\)
\(\Leftrightarrow3x+1=0\)
\(\Leftrightarrow3x=-1\)
hay \(x=-\frac{1}{3}\)
Vậy: \(x=-\frac{1}{3}\)
c) Ta có: \(x^2-6x=16\)
\(\Leftrightarrow x^2-6x-16=0\)
\(\Leftrightarrow x^2-8x+2x-16=0\)
\(\Leftrightarrow x\left(x-8\right)+2\left(x-8\right)=0\)
\(\Leftrightarrow\left(x-8\right)\left(x+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-8=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=8\\x=-2\end{matrix}\right.\)
Vậy: \(x\in\left\{8;-2\right\}\)
d) Ta có: \(9x^2+6x=80\)
\(\Leftrightarrow9x^2+6x-80=0\)
\(\Leftrightarrow9x^2+6x+1-81=0\)
\(\Leftrightarrow\left(3x+1\right)^2-9^2=0\)
\(\Leftrightarrow\left(3x+1-9\right)\left(3x+1+9\right)=0\)
\(\Leftrightarrow\left(3x-8\right)\left(3x+10\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}3x-8=0\\3x+10=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}3x=8\\3x=-10\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{8}{3}\\x=-\frac{10}{3}\end{matrix}\right.\)
Vậy: \(x\in\left\{\frac{8}{3};-\frac{10}{3}\right\}\)
e) Ta có: \(25\left(2x-1\right)^2-9\left(x+1\right)^2=0\)
\(\Leftrightarrow\left(10x-5\right)^2-\left(3x+3\right)^2=0\)
\(\Leftrightarrow\left(10x-5-3x-3\right)\left(10x-5+3x+3\right)=0\)
\(\Leftrightarrow\left(7x-8\right)\left(13x-2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}7x-8=0\\13x-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}7x=8\\13x=2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{8}{7}\\x=\frac{2}{13}\end{matrix}\right.\)
Vậy: \(x\in\left\{\frac{8}{7};\frac{2}{13}\right\}\)
\(x^3+9x^2+6x-16=\left(x^3+8x^2\right)+\left(x^2+8x\right)-\left(2x+16\right)\)
\(=x^2\left(x+8\right)+x\left(x+8\right)-2\left(x+8\right)\)
\(=\left(x+8\right)\left(x^2+x-2\right)\)
\(=\left(x+8\right)\left(x^2+2x-x-2\right)\)
\(=\left(x+8\right)\left(x+2\right)\left(x-1\right)\)
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