What is the equation with the difference of 54.57

What are the soultion(s) to the quadratic equation 40- x^2=0

How to choose the sign of the radical in the denominator of the formula for the distance from a point to a line.

Assume that there is a 11% rate of disk drive failure in a year. a. if all your computer data is stored on a hard disk drive with a copy stored on a second hard disk drive, what is the probability that during a year, you can avoid catastrophe with at least one working drive? b. if copies of all your computer data are stored on four independent hard disk drives, what is the probability that during a year, you can avoid catastrophe with at least one working drive?