1. \(\left(5x-y\right)^2\)
2. \(\left(x^2-2y\right)^2\)
3. \(\left(3x^2-2y\right)^2\)
4. \(\left(9^2-2x^3\right)^2\)
1/ \(25x^2-10xy+y^2=\left(5x\right)^2-2.5xy+y^2=\left(5x-y\right)^2\)
2/\(x^4-4x^2y+4y^2=\left(x^2\right)^2-2.x^2.2y+\left(2y\right)^2=\left(x^2-2y\right)^2\)
3/\(9x^4-12x^2y+4y^2=\left(3x^2\right)^2-2.3x^2.2y+4y^2=\left(3x^2-2y\right)^2\)
4/\(9x^4-12x^5+4x^6=\left(3x^2\right)^2-2.3x^2.2x^3+\left(2x^3\right)^2=\left(3x^2-2x^3\right)^2\)