Question

Answer 1

`(a-b)^2 = (a-b)(a-b) = a^2 - 2ab + b^2`

Vì `a, b in NN**`

`-> -2ab < 0`

`-> a^2 + b^2 > (a-b)^2`

Answer 2

\(a^2+b^2>\left(a-b\right)^2=a^2+b^2-2ab\left(vớia\in N^{\cdot},b\in N^{\cdot}\right)\)

Answer 3

\(\left(a-b\right)^2=a^2+b^2-2ab\) 

Vì a ; b \(\in N\) * \(\Rightarrow ab>0\) 

Do đó : \(a^2+b^2>\left(a-b\right)^2\)

Answer 4

 

Vì a : b * 

Vậy nên :