Range of f(x) =4^x+2^x+1 is?

Dear Dipankar,
Taking 2^x=m and solving the quadratic for getting D>=0
we get range= [3/4 , infinity )
ANS
Regards.

Actually the answer is (1,infinity)

hi dipankar 

domain of f(x) is (- infinity to + infinity )  and f(x) is INCREASING FUNCTION 

so the minimum value of f(x) will be f(- infinity ) that will be 1

and max value will be + infinite we know max value of a^x is + infinite

so the range is [ 1 , infinity[