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\(3\left(x^4+x^2+1\right)-\left(x^2+x+1\right)^2\)
\(=3\left(x^4+x^2+1\right)-\left(x^4+x^2+1+2x^3+2x^2+2x\right)\)
\(=2\left(x^4+x^2+1\right)-2\left(x^3+x^2+x\right)\)
\(=2\left(x^4+x^2+1-x^3-x^2-x\right)\)
\(=2\left(x^4-x^3-x+1\right)\)
\(=2\left(x^3\left(x-1\right)-\left(x-1\right)\right)\)
\(=2\left(x-1\right)\left(x^3-1\right)\)
\(=2\left(x-1\right)^2\left(x^2+x+1\right)\)
\(3\left(x^4+x^2+1\right)-\left(x^2+x+1\right)^2\)
\(=3\left[x^4+2x^2+1-x^2\right]-\left(x^2+x+1\right)^2\)
\(=3\left[\left(x^2+1\right)^2-x^2\right]-\left(x^2+x+1\right)^2\)
\(=3\left(x^2+x+1\right)\left(x^2-x+1\right)-\left(x^2+x+1\right)^2\)
\(=\left(x^2+x+1\right)\left(3x^2-3x+3-x^2-x-1\right)\)
\(=\left(x^2+x+1\right)\left(2x^2-4x+2\right)\)
\(=2\left(x-1\right)^2\cdot\left(x^2+x+1\right)\)
\(\left(x-1\right)^2=\left(x-1\right)\)
\(x1=1\)
\(x2=2\)
Dạ là \(\left(x+1\right)^4\)chứ ko phải \(\left(x+1^4\right)\)ạ
Còn \(\left(x^2+x+1\right)^2\)giữ nguyên ạ
Đặt \(x^2+x+1=t\)
\(\left(x^2+x+1\right)\left(x^2+x+2\right)-12=t\left(t+1\right)-12=t^2+t-12=\left(t^2+t+\dfrac{1}{4}\right)-\dfrac{49}{4}=\left(t+\dfrac{1}{2}\right)^2-\left(\dfrac{7}{2}\right)^2=\left(t+\dfrac{1}{2}-\dfrac{7}{2}\right)\left(t+\dfrac{1}{2}+\dfrac{7}{2}\right)=\left(t-3\right)\left(t+4\right)=\left(x^2+x-2\right)\left(x^2+x+5\right)\)
\(\left(x^2+x+1\right)\left(x^2+x+2\right)-12\)
= \(\left(x^2+x+1\right)\left[\left(x^2+x+1\right)+1\right]-12\)
= \(\left(x^2+x+1\right)^2\left(x^2+x+1\right)-12\)
= \(\left(x^2+x+1\right)\left(x^2+x+1\right)-3\left(x^2+x+1\right)+4\left(x^2+x+1\right)-4.3\)
= \(\left(x^2+x+1\right)\left(x^2+x-2\right)+4\left(x^2+x-2\right)\)
= \(\left(x^2+x+5\right)\left(x^2+x-2\right)\)
1. \(B=\left(x-2\right)\left(x+2\right)\left(x+3\right)-\left(x+1\right)^3\)
\(=\left(x^2-4\right)\left(x+3\right)-\left(x^3+3x^2+3x+1\right)\)
\(=x^3+3x^2-4x-12-x^3-3x^2-3x-1\)
\(=-7x-13\)
2. \(64-x^2-y^2+2xy=64-\left(x^2+y^2-2xy\right)\)
\(=64-\left(x-y\right)^2=\left(8+x-y\right)\left(8-x+y\right)\)
3. \(2x^3-x^2+2x-1=0\)
\(\Leftrightarrow x^2.\left(2x-1\right)+\left(2x-1\right)=0\)
\(\Leftrightarrow\left(2x-1\right)\left(x^2+1\right)=0\)
Vì \(x^2\ge0\)\(\Rightarrow x^2+1>0\)
\(\Rightarrow2x-1=0\)\(\Rightarrow2x=1\)\(\Rightarrow x=\frac{1}{2}\)
Vậy \(x=\frac{1}{2}\)
Bài 1.
B = ( x - 2 )( x + 2 )( x + 3 ) - ( x + 1 )3
= ( x2 - 4 )( x + 3 ) - ( x3 + 3x2 + 3x + 1 )
= x3 + 3x2 - 4x - 12 - x3 - 3x2 - 3x - 1
= -7x - 13
Bài 2.
64 - x2 - y2 + 2xy
= 64 - ( x2 - 2xy + y2 )
= 82 - ( x - y )2
= ( 8 - x + y )( 8 + x - y )
Bài 3.
2x3 - x2 + 2x - 1 = 0
<=> ( 2x3 - x2 ) + ( 2x - 1 ) = 0
<=> x2( 2x - 1 ) + 1( 2x - 1 ) = 0
<=> ( 2x - 1 )( x2 + 1 ) = 0
<=> \(\orbr{\begin{cases}2x-1=0\\x^2+1=0\end{cases}}\Leftrightarrow x=\frac{1}{2}\)( vì x2 + 1 ≥ 1 > 0 ∀ x )
Sai đề nhé bạn
\(\left(x^2+x+1\right)\left(x^2+x+2\right)-12\)
Đặt \(x^2+x+1=t\)
Đa thức trở thành \(t\left(t+1\right)-12\)
\(=t^2+t-12\)
\(=t^2+3t-4t-12\)
\(=t\left(t+3\right)-4\left(t+3\right)\)
\(=\left(t+3\right)\left(t-4\right)\)
Thay vào ta được
\(\left(x^2+x+4\right)\left(x^2+x-3\right)\)
Đặt: \(x^2-6x+1=a;x^2+1=b\)
Khi đó đa thức này có dạng:
\(2a^2+5ab+2b^2=2a^2+4ab+ab+2b^2\)
\(=2a\left(a+2b\right)+b\left(a+2b\right)=\left(a+2b\right)\left(2a+b\right)\)
Thay lại a và b thì được:
\(\left(a+2b\right)\left(2a+b\right)=\left(x^2-6x+1+2x^2+2\right)\left(2x^2-12x+2+x^2+1\right)\)
\(=\left(3x^2-6x+3\right)\left(3x^2-12x+3\right)\)
\(=9\left(x-1\right)^2\left(x^2-4x+1\right)\)
Vậy ...
\(x^2\left(x+1\right)=x+1\)
\(\Rightarrow x^2\left(x+1\right)-\left(x+1\right)=0\)
\(\Rightarrow\left(x+1\right)\left(x^2-1\right)=0\)
\(\Rightarrow\left(x+1\right)\left(x-1\right)\left(x+1\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x+1=0\\x-1=0\end{cases}\Rightarrow\orbr{\begin{cases}x=-1\\x=1\end{cases}}}\)
Vậy \(x=-1;x=1\)
TL:
\(x^2\left(x+1\right)=x+1\)
\(x^2\left(x+1\right)-\left(x+1\right)=0\)
\(\left(x^2-1\right)\left(x+1\right)=0\)
\(\left(x+1\right)^2\left(x-1\right)=0\)
\(\Rightarrow x-1=0\) hoặc \((x+1)^2=0\)
\(x=1\) hoặc \(x=-1\)
Vậy \(x\in\left\{1;-1\right\}\)
hc tốt