\(y^2-4x^2-2y+1\)
\(=\left(y-1\right)^2-4x^2\)
\(=\left(y+4x-1\right)\left(y-4x-1\right)\)
mình đổi dấu đó!
\(=y^2-2y+1-4x^2\)
\(=\left(y-1\right)^2-4x^2\)
\(=\left(y-1-4x\right).\left(y-1+4x\right)\)
y2 + 4x2 - 2y + 1
= ( y2 - 2y + 12 ) - ( 2x )2
= ( y - 1 )2 - ( 2x ) 2
= ( y - 1 - 2x ) ( y - 1 + 2x )