（3+a)²-(36-4a²)+4(3-a)² x²(3x+5Y)²-y²(5x+3y)² 感激不尽!

（3+a)²-(36-4a²)+4(3-a)² x²(3x+5Y)²-y²(5x+3y)² 感激不尽!
（3+a)²-(36-4a²)+4(3-a)² x²(3x+5Y)²-y²(5x+3y)² 感激不尽!

（3+a)²-(36-4a²)+4(3-a)² x²(3x+5Y)²-y²(5x+3y)² 感激不尽!
(3+a)^2-(36-4a^2)+4(3-a)^2
=(3+a)^2-4(9-a^2)+4(3-a)^2
=(3+a)^2-4(3+a)(3-a)+4(3-a)^2
=(3+a-2(3-a))^2
=(3a-3)^2
=9(a-1)^2
x^2(3x+5y)^2-y^2(5x+3y)^2
=[x(3x+5y)]^2-[y(5x+3y)]^2
=[x(3x+5y)+y(5x+3y)][x(3x+5y)-y(5x+3y)]
=(3x^2+5xy+5xy+3y^2)(3x^2+5xy-5xy-3y^2)
=(3x^2+10xy+3y^2)(3x^2-3y^2)
=3(3x^2+10xy+3y^2)(x^2-y^2)
=3(3x^2+10xy+3y^2)(x+y)(x-y)