Answer: [tex]\frac{511}{512}[/tex]
Explanation:
Let A represent "getting at least one head in 9 tosses"
Then  is "getting no heads in 9 tosses"
P(A) = 1 - P(Â)
 only occurs when all tosses are tails (TTT TTT TTT), so there is only one option of getting no heads.
There are a total of 2⁹ possible outcomes.
So, P(A) = 1 - [tex]\frac{1}{2^{9}}[/tex]
= [tex]\frac{2^{9}}{2^{9}}[/tex] - [tex]\frac{1}{2^{9}}[/tex]
= [tex]\frac{2^{9}-1}{2^{9}}[/tex]
= [tex]\frac{511}{512}[/tex]
