Question

if a²-4a-1=0 then a²+1/a²=?

Answer 1

a2 -4a =1 dividing by a
a-4=1/a
a-1/a=4
on squaring both sides
a2-2+1/a2=16
a2+1/a2=16+2=18

Answer 2

let solve it by formula method
a=1 b=-4 c=-1
so find valueof b^2—4ac
then
a=( (-b) plus minus (√b^2—4ac))/2a
then u will get two values of a or then put that values in a^2+1/a^2 u will get ur ans