The answer to this question is 0.9
We know that
sequre of 9 is equal to 81 as [tex]9^2 = 81[/tex]
Then sequre of 0.9 will be
[tex]0.9^2 = 0.81[/tex]
So,
b = [tex]\sqrt{ 0.81}[/tex]
b = [tex]\sqrt{ 0.9^2}[/tex]
Exponent and square root cancel out each other
So, the answer is 0.9.