①7x²-63
=7(x+3)(x-3)
②a²-a
=a(a-1)
③ 3²-3B²
=-3(B²-3)
=-3(B-√3)(B+√3)
④ y²-8（x+y)²
=(y+2√2(x+y))(y-2√2(x+y))
分解因式 ①7x²-63 ②a²-a ③ 3²-3B² ④ y²-8（
①7x²-63
=7(x+3)(x-3)
②a²-a
=a(a-1)
③ 3²-3B²
=-3(B²-3)
=-3(B-√3)(B+√3)
④ y²-8（x+y)²
=(y+2√2(x+y))(y-2√2(x+y))