Question

can someone help answer these questions thank you !

Answer 1

Answer:

Step-by-step explanation:

4) (a - b)² = a² - 2ab + b²

$(5-\sqrt{5})^{2}=5^{2}-2*5*\sqrt{5}+(\sqrt{5})^{2}\\\\ =25-10\sqrt{5}+5\\\\=30-10\sqrt{5}$

5) Use FOIL method.

$(1+\sqrt{2})(3-\sqrt{2})=(1*3)+1*(-\sqrt{2})+\sqrt{2}*3+\sqrt{2}*(-\sqrt{2})\\\\ =3-\sqrt{2}+3\sqrt{2}-2\\\\=3-2-\sqrt{2}+3\sqrt{2}\\\\=1-2\sqrt{2}$