Question

Answer 1

`(2a+1)^2-16(a+1)^2`

`=(2a+1)^2-(4a+4)^2`

`=(2a+1-4a-4)(2a+1+4a+4)=(-2a-3)(6a+5)`

   `=>` Chỗ cần điền là: `6`

______________________________

`(x+y)^3-3xy(x+y)`

`=(x+y)[(x+y)^2-3xy]`

`=(x+y)(x^2+2xy+y^2-3xy)`

`=(x+y)(x^2-xy+y^2)=x^3+y^3`

  `=>a=1;b=1`

 `=>a-b=1-1=0`