phân tích đa thức thành nhân tử :
\(-2x^2-4x+30\)
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\(1,=x\left(x^2-2x+1-y^2\right)=x\left[\left(x-1\right)^2-y^2\right]=x\left(x-y-1\right)\left(x+y-1\right)\\ 2,=\left(x+y\right)^3\\ 3,=\left(2y-z\right)\left(4x+7y\right)\\ 4,=\left(x+2\right)^2\\ 5,Sửa:x\left(x-2\right)-x+2=0\\ \Leftrightarrow\left(x-2\right)\left(x-1\right)=0\Leftrightarrow\left[{}\begin{matrix}x=1\\x=2\end{matrix}\right.\)
#)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:
\(x^3-2x-4\)
\(=x^3-2x^2+2x^2-4x+2x-4\)
\(=x^2\left(x-2\right)+2x\left(x-2\right)+2\left(x-2\right)\)
\(=\left(x-2\right)\left(x^2+2x+2\right)\)
\(a,2x^3y-2xy=2xy\left(x^2-1\right)=2xy\left(x-1\right)\left(x+1\right)\)
\(b,x^2-2x-4x^2-4x=-3x^2-2x-4x\\ =-3x^2-6x=-3\left(x^2+2x\right)=-3x\left(x+2\right)\)
\(=\left(2x-5\right)\left(2x+5\right)-\left(2x-5\right)\left(2x+7\right)\)
\(=\left(2x-5\right)\left(2x+5-2x-7\right)\)
\(=-2\left(2x-5\right)\)
\(x^4+4x^3+2x^2-4x+1\)
\(=x^4+2x^3-x^2+2x^3+4x^2-2x-x^2-2x+1\)
\(=x^2\left(x^2+2x-1\right)+2x\left(x^2+2x-1\right)-\left(x^2+2x-1\right)\)
\(=\left(x^2+2x-1\right)^2\)
2x2 + 4x + 2 - 2y2
= 2(x + 1)2 - 2y2
= 2(y + x + 1)(x + 1 - y)
\(2x^2+4x+2-2y^2\)
\(=2\left(x^2+2x+1-y^2\right)\)
\(=2\left[\left(x+1\right)^2-y^2\right]\)
\(=2\left(x+1+y\right)\left(x+1-y\right)\)
Hok tốt!
\(x^4-4x^3-2x^2-3x+2\)
\(\Leftrightarrow x^4+x^3-5x^3+x^2-5x^2+2x^2-5x+2x+2\)
\(\Leftrightarrow x^4+x^3+x^2-5x^3-5x^2-5x+2x^2+2x+2\)
\(\Leftrightarrow x^2\left(x^2+x+1\right)-5x\left(x^2+x+1\right)+2\left(x^2+x+1\right)\)
\(\Leftrightarrow\left(x^2-5x+2\right)\left(x^2+x+1\right)\)
Xin tick ạ !!!
= ( 2x - 5 )(2x + 5) - ( 2x- 5 )(2x + 7 )
= (2x - 5 ) [ 2x+ 5 - ( 2x+ 7 ) ]
= ( 2x- 5 ) ( 2x + 5 - 2x - 7 )
= - 2( 2x- 5 )
= -2 ( x2 + 2x + 1 ) + 32
= -2 ( x +1 )2 + 32
= - 2 [ (x + 1 )2 - 16 ]
= -2 [ (x + 1 ) 2 - 42 ]
= -2 ( x + 1 - 4 ) ( x + 1 + 4)
= -2 ( x - 3 ) ( x +5 )
\(-2x^2-4x+30\)
\(=-2\left(x^2+2x+1\right)+32\)
\(=-2\left(x+1\right)^2+32\)
\(=-2\left[\left(x+1\right)^2-16\right]\)
\(=-2\left[\left(x+1\right)^2-4^2\right]\)
\(=-2\left(x+1-4\right)\left(x+1+4\right)\)
\(=-2\left(x-3\right)\left(x+5\right)\)