a,Ta có:(x+2)²-x.(x-1)
=x²+4x+4-x²+x
=5x+4
KL:Vậy:(x+2)²-x.(x-1)=5x+4
b,Ta có:(2x-3)²-2.(2x-3).(x+1)+(x-1)²
=4x²-12x+9-2.(2x²+2x-3x-3)+x²-2x+1
=4x²-12x+9-4x²-4x+6x+6+x²-2x+1
=-12x+10
KL:Vậy:(2x-3)²-2.(2x-3).(x+1)+(x-1)²=-12x+10
Hằng đẳng thức:(a+b)²=a²+2ab+b²
(a-b)²=a²-2ab+b²
#Nocopy