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\(x^2-4x+4-y^2\)
\(=\left(x-2\right)^2-y^2\)
\(=\left(x-2-y\right)\left(x-2+y\right)\)
\(x^2-4x+4-y^2\)
\(=\left(x-2\right)^2-y^2\)
\(=\left(x-2-y\right)\left(x-2+y\right)\)
\(=\left(x-y\right)^2-2\left(x-y\right)=\left(x-y\right)\left(x-y-2\right)\)
Ta có
a, x2-x-y2-y
=x2-y2-(x+y)
=(x-y)(x+y) - (x+y)
=(x+y)(x-y-1)
b, x2-2xy+y2-z2
=(x-y)2-z2
=(x-y-z)(x-y+z)
\(x^3-64=x^3-4^3\)
\(\Rightarrow\left(x-4\right)\left(x^2+4x+4^2\right)\)
\(x^4+1997x^2+1996x+1997=x^4+1997x^2+1997x-x+1997=\left(x^4-x\right)+1997\left(x^2+x+1\right)=x\left(x-1\right)\left(x^2+x+1\right)+1997\left(x^2+x+1\right)=\left(x^2-x+1997\right)\left(x^2+x+1\right)\)
\(x^4+1997x^2+1996x+1997\\ =x^4+x^3+x^2-x^3-x^2-x+1997x^2+1997x+1997\)
\(=\left(x^4+x^3+x^2\right)-\left(x^3+x^2+x\right)+\left(1997x^2+1997x+1997\right)\)
\(=x^2\left(x^2+x+1\right)-x\left(x^2+x+1\right)+1997\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right)\left(x^2-x+1997\right)\)
x^2 + 7x -15
= x^2 + 7x +12,25 -27,25
= (x+3,5)^2 - 27, 25
= ( x+3,5 - \(\sqrt{27,25}\))(x+3,5+\(\sqrt{27,25}\))
= (x-y)(x+y)-(x+y)
=(x+y)(x-y-1)
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