Question

can anybody please help me with this?

Answer 1

\[\left( a-b \right)^{2}=a ^{2}+b ^{2}-2ab\]

Answer 2

\[(a-b)^2=a^2-2ab+b^2\rightarrow \left( \sqrt{14} -2\sqrt{2}\right)^2=14-4\sqrt{28}+8=\]\[22-8\sqrt{7}\]

Answer 3

thanks a lot :)