Ta có: \(x^2-3xy+y^2\)
\(=x^2-2\cdot x\cdot\frac32y+\left(\frac32y\right)^2-\left(\frac32y\right)^2+y^2\)
\(=\left(x-\frac32y\right)^2-\frac54y^2\)
\(=\left(x-\frac32y-\frac{y\sqrt5}{2}\right)\left(x-\frac32y+\frac{y\sqrt5}{2}\right)\)
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