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\(x^4+2x^2-24\)
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\(b,=x^4-2x^3-x^3+2x^2+3x^2-6x-3x+6\\ =\left(x-2\right)\left(x^3-x^2+3x-3\right)\\ =\left(x-2\right)\left(x-1\right)\left(x^2+3\right)\\ c,=x^4-2x^3+4x^3-8x^2+4x^2-8x+3x-6\\ =\left(x-2\right)\left(x^3+4x^2+4x+3\right)\\ =\left(x-2\right)\left(x^3+3x^2+x^2+3x+x+3\right)\\ =\left(x-2\right)\left(x+3\right)\left(x^2+x+1\right)\)
#)Giải :
\(x^3-2x-4\)
\(=x^3+2x^2-2x^2+2x-4x-4\)
\(=x^3+2x^2+2x-2x^2-4x-4\)
\(=x\left(x^2+2x+2\right)-2\left(x^2+2x+2\right)\)
\(=\left(x-2\right)\left(x^2+2x+2\right)\)
\(x^4+2x^3+5x^2+4x-12\)
\(=x^4+x^3+6x^2+x^3+x^2+6x-2x^2-2x-12\)
\(=x^2\left(x^2+x+6\right)+x\left(x^2+x+6\right)-2\left(x^2+x+6\right)\)
\(=\left(x^2+x+6\right)\left(x^2+x-2\right)\)
\(=\left(x^2+x+6\right)\left(x-1\right)\left(x+2\right)\)
Câu 1.
Đoán được nghiệm là 2.Ta giải như sau:
\(x^3-2x-4\)
\(=x^3-2x^2+2x^2-4x+2x-4\)
\(=x^2\left(x-2\right)+2x\left(x-2\right)+2\left(x-2\right)\)
\(=\left(x-2\right)\left(x^2+2x+2\right)\)
\(x^4+2x^2-24\)
\(=x^4+6x^2-4x^2-24\)
\(=x^2\left(x^2+6\right)-4\left(x^2+6\right)\)
\(=\left(x^2+6\right)\left(x^2-4\right)\)
\(=\left(x^2+6\right)\left(x-2\right)\left(x+2\right)\)
\(x^3-2x-4\)
\(=x^3-2x^2+2x^2-4x+2x-4\)
\(=x^2\left(x-2\right)+2x\left(x-2\right)+2\left(x-2\right)\)
\(=\left(x-2\right)\left(x^2+2x+2\right)\)
Chúc bạn học tốt.
( x2 - 3x )2 + ( 2x2 - 6x ) - 24
= ( x2 - 3x )2 + 2( x2 - 3x ) - 24 (*)
Đặt t = x2 - 3x
(*) trở thành :
t2 + 2t - 24
= t2 - 4t + 6t - 24
= t( t - 4 ) + 6( t - 4 )
= ( t - 4 )( t + 6 )
= ( x2 - 3x - 4 )( x2 - 3x + 6 )
= ( x2 + x - 4x - 4 )( x2 - 3x + 6 )
= [ x( x + 1 ) - 4( x + 1 ) ]( x2 - 3x + 6 )
= ( x + 1 )( x - 4 )( x2 - 3x + 6 )
\(\left(x^2-3x\right)^2+\left(2x^2-6x\right)-24\)
\(=\left(x^2-3x\right)^2+2\left(x^2-3x\right)-24\)(1)
Đặt \(a=x^2-3x\)
(1)=\(a^2+2a-24\)
\(=a^2-4a+6a-24\)
\(=a\left(a-4\right)+6\left(a-4\right)\)
\(=\left(a-4\right)\left(a+6\right)\)
\(=\left(x^2-3x-4\right)\left(x^2-3x+6\right)\)
\(=\left(x^2-4x+x-4\right)\left(x^2-3x+6\right)\)
\(=\left[x\left(x-4\right)+\left(x-4\right)\right]\left(x^2-3x+6\right)\)
\(=\left(x+1\right)\left(x-4\right)\left(x^2-3x+6\right)\)
\(1,=x\left(x^2-2x+1-y^2\right)=x\left[\left(x-1\right)^2-y^2\right]=x\left(x-y-1\right)\left(x+y-1\right)\\ 2,=\left(x+y\right)^3\\ 3,=\left(2y-z\right)\left(4x+7y\right)\\ 4,=\left(x+2\right)^2\\ 5,Sửa:x\left(x-2\right)-x+2=0\\ \Leftrightarrow\left(x-2\right)\left(x-1\right)=0\Leftrightarrow\left[{}\begin{matrix}x=1\\x=2\end{matrix}\right.\)
Ta có : \(\left(x+1\right)\left(x+2\right)\left(x+3\right)\left(x+4\right)-24\)
\(=\left(\left(x+1\right)\left(x+4\right)\right)\left(\left(x+2\right)\left(x+3\right)\right)-24\)
\(=\left(x^2+5x+4\right)\left(x^2+5x+6\right)-24\)
- Đặt \(x^2+5x+5=a\)
\(=\left(a-1\right)\left(a+1\right)-24=a^2-1-24=a^2-25\)
\(=\left(a-5\right)\left(a+5\right)\)
\(=\left[\left(x+2\right)\left(x+5\right)\right]\left[\left(x+3\right)\left(x+4\right)\right]-24\\ =\left(x^2+7x+10\right)\left(x^2+7x+12\right)-24\\ =\left(x^2+7x+11\right)^2-1-24\\ =\left(x^2+7x+11\right)^2-25\\ =\left(x^2+7x+11-5\right)\left(x^2+7x+11+5\right)\\ =\left(x^2+7x+6\right)\left(x^2+7x+16\right)\\ =\left(x+1\right)\left(x+6\right)\left(x^2+7x+16\right)\)
\(x^4+2x^2-24\)
Đặt \(t=x^2\) ta có:
\(t^2+2t-24=t^2-4t+6t-24\)
\(=t\left(t-4\right)+6\left(t-4\right)\)
\(=\left(t+6\right)\left(t-4\right)\)
\(=\left(x^2+6\right)\left(x^2-4\right)\)
\(=\left(x-2\right)\left(x+2\right)\left(x^2+6\right)\)