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\(1,=x\left(x^2-2x+1-y^2\right)=x\left[\left(x-1\right)^2-y^2\right]=x\left(x-y-1\right)\left(x+y-1\right)\\ 2,=\left(x+y\right)^3\\ 3,=\left(2y-z\right)\left(4x+7y\right)\\ 4,=\left(x+2\right)^2\\ 5,Sửa:x\left(x-2\right)-x+2=0\\ \Leftrightarrow\left(x-2\right)\left(x-1\right)=0\Leftrightarrow\left[{}\begin{matrix}x=1\\x=2\end{matrix}\right.\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a,Từ giả thiết ta có
(x2+y2+z2)(x+y+z)2+(xy+yz+zx)2
=(x2+y2+z2)(x2+y2+z2+2xy+2yz+2zx)+(xy+yz+zx)2
Đặt x2+y2+z2=a
xy+yz+zx=b
=>(x2+y2+z2)(x2+y2+z2+2xy+2yz+2zx)+(xy+yz+zx)2
=a(a+2b)+b2
=a2+2ab+b2
=(a+b)2
=(x2+y2+z2+xy+yz+zx)2
câu b hơi dài mình gửi sau nhé
Ta có: 2(x^4+y^4+z^4)-(x^2+y^2+z^2)^2-2(x^2+y^2+z^2)(x+y+z)^2+(x+y+z)^4
Gọi x^4+y^4+z^4=a
x^2+y^2+z^2=b
x+y+z=c
=>2(x^4+y^4+z^4)-(x^2+y^2+z^2)^2-2(x^2+y^2+z^2)(x+y+z)^2+(x+y+z)^4=2a-b^2-2bc^2+c^4
=2a-2b^2+b^2-2bc^2+c^4
=2(a-b^2)+(b+c^2)^2
Ta có
2(a-b2)=2[x^4+y^4+z^4-(x^2+y^2+z^2)2]
=2[x^4+y^4+z^4-x^4-y^4-z^4-2x2y2-2y2z2-2z2x2]
=2.(-2)(x2y2+y2z2+z2x2)
=-4(x2y2+y2z2+z2x2)
Lại có
(b+c^2)^2
=[(x^2+y^2+z^2)+(x+y+z)2]2
=[(x^2+y^2+z^2)-(x^2+y^2+z^2)-2(xy+yz+zx)]2
=4(xy+yz+zx)2
=>2(a-b^2)+(b+c^2)^2
=-4(x2y2+y2z2+z2x2)+4(xy+yz+zx)2
=8xyz(x+y+z)
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\(1,\\ a,=4\left(x-2\right)^2+y\left(x-2\right)=\left(4x-8+y\right)\left(x-2\right)\\ b,=3a^2\left(x-y\right)+ab\left(x-y\right)=a\left(3a+b\right)\left(x-y\right)\\ 2,\\ a,=\left(x-y\right)\left[x\left(x-y\right)^2-y-y^2\right]\\ =\left(x-y\right)\left(x^3-2x^2y+xy^2-y-y^2\right)\\ b,=2ax^2\left(x+3\right)+6a\left(x+3\right)\\ =2a\left(x^2+3\right)\left(x+3\right)\\ 3,\\ a,=xy\left(x-y\right)-3\left(x-y\right)=\left(xy-3\right)\left(x-y\right)\\ b,Sửa:3ax^2+3bx^2+ax+bx+5a+5b\\ =3x^2\left(a+b\right)+x\left(a+b\right)+5\left(a+b\right)\\ =\left(3x^2+x+5\right)\left(a+b\right)\\ 4,\\ A=\left(b+3\right)\left(a-b\right)\\ A=\left(1997+3\right)\left(2003-1997\right)=2000\cdot6=12000\\ 5,\\ a,\Leftrightarrow\left(x-2017\right)\left(8x-2\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=2017\\x=\dfrac{1}{4}\end{matrix}\right.\\ b,\Leftrightarrow\left(x-1\right)\left(x^2-16\right)=0\Leftrightarrow\left[{}\begin{matrix}x=1\\x=4\\x=-4\end{matrix}\right.\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a, \(4\left(x+y+z\right)^2-9\left(x-y-z\right)^2\)
\(=\left[2\left(x+y+z\right)\right]^2-\left[3\left(x-y-z\right)\right]^2\)
\(=\left[2x+2y+2z\right]^2-\left[3x-3y-3z\right]^2\)
\(=\left[\left(2x+2y+2z\right)-\left(3x-3y-3z\right)\right].\left[\left(2x+2y+2z\right)+\left(3x-3y-3z\right)\right]\)
\(=\left(-x+5y+5z\right)\left(5x-y-z\right)\)
b, \(25\left(x-3y\right)^2-4\left(x+3y\right)^2\)
\(=\left[5\left(x-3y\right)\right]^2-\left[2\left(x+3y\right)\right]^2\)
\(=\left[5x-15y\right]^2-\left[2x+6y\right]^2\)
\(=\left[5x-15y-2x-6y\right].\left[5x-15y+2x+6y\right]\)
\(=\left(3x-21y\right)\left(7x-9y\right)\)
\(=3\left(x-7y\right)\left(7x-9y\right)\)
Chúc bạn học tốt.
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\(a,=\left(4x^2\right)^2\left(x-y\right)-\left(x-y\right)\)
\(=\left[\left(4x^2\right)^2-1^2\right]\left(x-y\right)\)
\(=\left(4x^2+1\right)\left(4x^2-1\right)\left(x-y\right)\)
\(=\left(4x^2+1\right)\left(2x+1\right)\left(2x-1\right)\left(x-y\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
b: \(=\dfrac{12\left(y-z\right)^4+3\left(y-z\right)^5}{6\left(y-z\right)^2}=2\left(y-z\right)^2+\dfrac{1}{2}\left(y-z\right)^3\)
![](https://rs.olm.vn/images/avt/0.png?1311)
x2(y - z) + y2(z - x) + z2(x - y)
= z2(x - y) + x2 y - x2 z + y2 z - y2 x
= z2(x - y) + (x2 y - y2 x) + (- x2 z + y2 z)
= (x - y)(z2 + xy - zx - zy)
= (x - y)[(z2 - zx) + (xy - zy)]
= (x - y)(z - x)(z -y)
\(x^2\left(y-z\right)+y^2\left(z-x\right)+z^2\left(x-y\right)\)
\(=x^2\left(y-z\right)+y^2\left(z-y+y-x\right)\)
\(=x^2\left(y-z\right)-y^2\left(y-z\right)-y^2\left(x-y\right)+z^2\left(x-y\right)\)
\(=\left(x-y\right)\left(x+y\right)\left(y-z\right)+\left(z-y\right)\left(y+z\right)\left(x-y\right)\)
\(=\left(x-y\right)\left(y-x\right)\left(x-z\right)\)
10x2y2