8a³-b³
=(2a)³-b³
=(2a-b)(4a²+2ab+b²)
x²-2x-1
=(x-1)²-2
=(x-1+√2)(x-1-√2)
4(x-y+1)+y(y-2x）
=4x-4y+4+y²-2xy
=(y²-4y+4)+4x-2xy
=(y-2)²+2x(2-y)
=(y-2)²-2x(y-2)
=(y-2)(y-2-2x)
=(y-2)(y-2x-2)
a²-zab+b²-za+2b-3 題抄錯了 z應(yīng)是2
a²-2ab+b²-2a+2b-3
=(a-b)²-2(a-b)-3
=(a-b+1)(a-b-3)
4x²+4xy-y²
=(4x²＋4xy＋y²)－2y²
=(2x＋y)²－2y²
=(2x＋y＋√2y)(2x＋y－√2y)
a³+1
=(a+1)(a²-a+1)