1.
If α,β\alpha, \beta are roots of the equation x2+52 x+10=0x^2 + 5\sqrt{2}\,x + 10 = 0, α>β\alpha > \beta and Pn=αn−βnP_n = \alpha^n - \beta^n for each positive integer nn, then the value of
P17 P20+52 P17 P19P18 P19+52 P17 P18\dfrac{P_{17}\,P_{20} + 5\sqrt{2}\,P_{17}\,P_{19}}{P_{18}\,P_{19} + 5\sqrt{2}\,P_{17}\,P_{18}}

is equal to: