Question

if a+1/a=3,then a^3+1/a^3=​

Answer 1

(a + 1/a) = 3
(a + 1/a)^3 = 3^3
a^3 + 3*a* 1/a(a+1/a)+ 1/a^3 = 27
a^3 + 3(3)+ 1/a^3 = 27
a^3+9 + 1/a^3 = 27
a^3+1/a^3= 27-9
a^3+1/a^3=18