1.27a^2-3
=3（9a²-1)
=3(3a+1)(3a-1)
2.9x^2-y^2
=(3x+y)(3x-y)
3.x^4-1
=(x²+1)(x²-1)
=(x²+1)(x+1)(x-1)
4.3x^2-18x+27
=3(x²-6x+9)
=3（x-3)²
5.a^2+a+四分之一
=(a+1/2)²
6.2x^3-8x^2y+8xy^2
=2x(x²-4xy+4y²)
=2x(x-2y)²
7.a^2(a-b)^2-(b-a)^2
=a²(a-b)²-(a-b)²
=(a-b）²（a²-1)
=(a-b)²(a+1)(a-1)
8.49(a-b)+y^2(b-a)
=49(a-b)-y²(a-b)
=(a-b)(49-y²)
=(a-b)(7+y)(7-y)