X2-3x+2
X2+4x-12
X2-(a+b)x+ab
X3+9+3x2+3x
B2+c2+2ab+2ac+2bc
怎么解
X2-3x+2
X2+4x-12
X2-(a+b)x+ab
X3+9+3x2+3x
B2+c2+2ab+2ac+2bc
怎么解
解:
X2-3x+2=(x-2)(x-1),
X2+4x-12=(x+6)(x-2),
X2-(a+b)x+ab=(x-a)(x-b),
X3+9+3x2+3x
=(X3+3x2)+(3x+9)
=(x+3)x2+3(x+3)
=(x+3)(x2+3)。
【B2+c2+2ab+2ac+2bc ??】.
a2+b2+c2+2ab+2ac+2bc
=(a2+b2+2ab)+(2ac+2bc)+c2
=(a+b)2+2c(a+b)+c2
=[(a+b)+c]2
=(a+b+c)2。