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

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

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

7(x+3)(x-3)
a(a-1)
3(3^(x-1)-b^x)

瞎糊弄人吧?

7x^2-63=7(x^2-3^2)=7(x+3)(x-3)
a^2-a=a(a-1)
3^2-3b^2=3^2-(根号3b)^2=(3+根号3)(3-根号3)
y^2-8(x+y)^2=y^2-(根号8(x+y))^2
=(y-2根号2(x+y))(y+2根号2(x+y))
=[(1-2根号2)y-2根号2x][(1+2根号2)y+2根号2x]