Đáp án:
Giải thích các bước giải:
1.(x+1).(x ²-x+1)-(x-1).(x ²+xy)
⇔ x³-x²+x+x²-x+1-(x³+x²y-x²-xy)
⇔ x³-x²+x+x²-x+1-x³-x²y+x²+xy
⇔x²-x²y+xy+1
2.(x-1 ) ³ - (x+1) ³ +6(x-1). (x+1)
⇔ x³-3x²+3x-1-( x³+3x²+3x+1)+6.(x²-1)
⇔x³-3x²+3x-1-x³-3x²-3x+1+6x²-6
⇔-8
3.(x+5) ² - (x-5) ² -20x + 2
⇔ x²+10x+25 - (x²-10x+25)-20x+2
⇔x²+10x+25 -x²+10x-25-20x+2
⇔2
4.(2x +6) . (4x ² -12x +36) -8x +5
⇔(2x)³+6³-8x+5
⇔8x³+216-8x+5
⇔8x³-8x+221
chúc bạn học tốt !!