Đáp án:
Giải thích các bước giải:
a) x²-y²-2x+2y=(x-y).(x+y)-2(x-y)=(x-y).(x+y-2)
b) 2x+2y-x²-xy=2.(x+y)-x.(x+y)=(x+y).(2-x)
c) 3a²-6ab+3b²-12c²=3(a²-2ab+b²-4c²)=3[(a-b)²-4c²]=3.(a-b-2c).(a-b+2c)
d) x²-25+y²+2xy=(x²+2xy+b²)-25=(x+y)²-25=(x+y-5).(x+y+5)
e) a²+2ab+b²-ac-bc=(a+b)²-c.(a+b)=(a+b).(a+b-c)
f) x²-2x-4y²-4y=x²-2x+1-4y²-4y-1=(x-1)²-(2y+1)²=(x-1-2y-1).(x-1+2y+1)=(x-2y-2).(x+2y)
g) x²y-x³-9y+9x=x²y-9y-x³+9x=y.(x²-9)-x.(x²-9)=(x²-9).(y-x)=(x-3).(x+3).(y-x)
h) x²(x-1)+16(1-x)=x²(x-1)-16(x-1)=(x-1).(x²-16)=(x-1).(x-4).(x+4)
n) 81x²-6yz-9y²-z²=
m) xz-yz-x²+2xy-y²=z(x-y)-(x-y)²=(x-y).(z-x+y)
p) x²+8x+15=x²+5x+3x+15=x(x+5)+3(x+5)=(x+5).(x+3)
k) x²-x-12=x²-4x+3x-12=x(x-4)+3(x-4)=(x-4)(x+3)
l) 81x^4+4=81x^4+36x²+4-36x²=(9x²+2)²-36x²=(9x²+2-6x).(9x²+2+6x)
