Radicals picture attached below

The formula

represents the length of the hypotenuse of a right triangle with side lengths a and b, and we have to solve for b .

First we need to get rid of the radical and for that, we do squaring on both sides. That is

Now we need to get rid of a^2 and for that we do subtraction.

And finally we need to get rid of square, and for that we take radical to both sides

or