2. Упростите: 1) √7 + (√28 − √63); 2) (1 − √2)(3 + √2); 3) (√3 − 2√7)(2√7 + √3).

1. \(\sqrt{7}+\sqrt{28}-\sqrt{63}=\sqrt{7}+2\sqrt{7}-3\sqrt{7}=0\), поскольку \(\sqrt{28}=2\sqrt{7}\), а \(\sqrt{63}=3\sqrt{7}\).
2. \((1-\sqrt{2})(3+\sqrt{2})=3+\sqrt{2}-3\sqrt{2}-2=1-2\sqrt{2}\).
3. \((\sqrt{3}-2\sqrt{7})(2\sqrt{7}+\sqrt{3})=(\sqrt{3}-2\sqrt{7})(\sqrt{3}+2\sqrt{7})=3-(2\sqrt{7})^2=3-28=-25\).

Ответ: 1) 0; 2) 1 − 2√2; 3) −25.