Phan tich thanh nhan tu:
\(x^2+2xy-8y^2+2xz+14yz-3z^2\)
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x2 + 2xy - 8y2 + 2xz + 14yz - 3z2
= ( x2 + y2 +z2 + 2xy + 2yz ) + ( -9x2 + 12yz - 4x2 )
= ( x + y +z )2 - [ (3x)2 - 2.3.x.2y + ( 2x)2
= ( x + y +z )2 - ( 3y - 2x)2
= ( x + y +z - 3y + 2x )(x+ y + z + 3y - 2x )
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)
\(=3^2-\left(x-y\right)^2=\left[3-\left(x-y\right)\right]\left[3+\left(x-y\right)\right]=\left(3-x+y\right)\left(3+x-y\right)\)
\(9-x^2+2xy-y^2\)
\(=9-\left(x^2-2xy+y^2\right)\)
\(=3^2-\left(x-y\right)^2\)
\(=\left(3-x+y\right)\left(3-x-y\right)\)
x^2-2xy+y^2-9z^2
=(x-y)^2-9z^2
=(x-y)^2-(3z)^2
=(x-y-3z)(x-y+3z)
\(x^2+2xy-8y^2+2xz+14yz-3z^2\)
\(=\left(x^2+y^2+z^2+2xy+2xz+2yz\right)+\left(-9x^2+12yz-4x^2\right)\)
\(=\left(x+y+z\right)^2-\left[\left(3x\right)^2-2.3x.2y+\left(2x\right)^2\right]\).
\(=\left(x+y+z\right)^2-\left(3y-2x\right)^2\)
\(=\left(x+y+z-3y+2x\right)\left(x+y+z+3y-2x\right)\)