Cho a,b,x,y [tex]\in R[/tex] sao cho: ax + by = 3 [tex]ax^{2}+by^{2}=5[/tex] [tex]ax^{3}+by^{3}=9[/tex] [tex]ax^{4}+by^{4}=17[/tex] Tính [tex]A= ax^{5}+by^{5}[/tex]