9(x+y)²-4(x-y)²=?

9(x+y)²-4(x-y)²=?
9(x+y)²-4(x-y)²=?

9(x+y)²-4(x-y)²=?
因式分解?
9(x+y)²-4(x-y)²
=[3(x+y)+2(x-y)]*[3(x+y)-2(x-y)]
=(5x+y)(x+5y)
计算?
9(x+y)²-4(x-y)²
=9x²+18xy+9y²-4x²+8xy-4y²
=5x²+26xy+5y²