Question

( begin{aligned} frac{4+sqrt{5}}{4-sqrt{5}}+frac{4-sqrt{5}}{4+sqrt{5}} &=frac{(4+sqrt{5})^{2}+(4-sqrt{5})^{2}}{(4-sqrt{5})(4+sqrt{5})} &=16+5+frac{8 sqrt{5}+16+5-8 sqrt{5}}{16-5} &=frac{42}{11} end{aligned} )

# UU 4+5,4-5 牛 - 5 45

Solution