` x^2 (x^2 + 1) + 1 `
` = x^4 + x^2 + 1 `
` = x^4 + 2x^2 + 1 - x^2 `
` = (x^2 + 1) - x^2 `
` = (x^2 + 1 - x)(x^2 + 1 + x) `
` x^{3}y - 3xy + 2y `
` = y(x^3 - 3x + 2) `
` = y(x^3 - x - 2x + 2) `
` = y[x(x - 1)(x + 1) - 2(x - 1)] `
` = y(x - 1)[x(x + 1) - 2] `
` = y(x - 1)(x^2 + x - 2) `
` = y(x - 1)(x^2 - x + 2x - 2) `
` = y(x - 1)[x(x - 1) + 2(x - 1)] `
` = y(x - 1)(x - 1)(x + 2) `
` = y(x - 1)^2 (x + 2) `
