A virus is very small compared to a human blood cell. A virus is about 0.0000009 meters. What is that in scientific notation?

Can someone me with my hwplz(only the circled ones)

Given the function f(x) = log base 4(x+8) , find the value of f^-1(2)

Which of the following equations is of the parabola whose vertex is at (2, 3), axis of symmetry parallel to the y-axis and p = 4? a.)y-3 = 1/16 (x-2)^2 b.)y+3 = -1/16 (x+2)^2 c.)x-2 = 1/16 (y-3)^2