x^2 - (y^2 - 4y + 4)
= x^2 - (y - 2)^2
= (x - y + 2)(x + y - 2)如果可以，在告訴我。（X+Y）2+4XY（X+Y）2-4（X+Y-1）（X-1）（X-3）+1ax-bx+ay-by告訴我可又獎勵(x + y)² + 4xy= x² + 2xy + y² + 4xy= x² + 6xy + y²= x² + 6xy + 9y² - 8y²= (x + 3y)² - (√8y)²= (x + 3y + 2√2y)(x + 3y - 2√2y)(x + y)² - 4(x + y - 1)= (x + y)² - 4(x + y) + 4= [(x + y) - 2]²= (x + y - 2)²(x - 1)(x - 3) + 1= x² - 4x + 4= (x - 2)²x^2 - (y^2 - 4y + 4)= x^2 - (y - 2)^2這是怎么來的4Y呢運用(a - b)² = a² - 2ab + b²還有a² - b² = (a + b)(a - b)