How do you solve #x^2=90#?
Taking the square root of any number gives you two answers, one positive and one negative e.g. -2 x -2 =4
Square root of 90 = square root of 9 x 10
You can root the 3 to give 3
Using the 'Principle square root'. That is, the positive one.
Square root both sides
Not that the decimal equivalent would be rounded and thus not as precise.