Đáp án + Giải thích các bước giải:
Bài `12:`
`a) x^2-y^2 =(x-y). (x+y)=(87+13).(87-13)=100.74`
`=7400`
`b) x^3-3x^2+3x-1=x^3-3x^2.1+3x1^2-1^3=(x-1)^3`
`=(101-1)^3=100^3`
`=1000000`
`c) x^3+9x^2+27x+27=x^3+3x^2.3+3^2+3^3`
`=(x+3)^3=(97+3)^3=100^3`
`=1000000`
`d) x^3+3x^2+3x=x^3+3x^2+3x+1-1`
`=(x+1)^3-1=(99+1)63-1`
`=999999`
`text{#Study Well}`