How are expressions and equations different ?

The primary difference between equations and expressions is equal signs. An "equation" has a left side, a right side and an equals sign separating the sides. An expression however, we are not expected to do or solve anything.

For example:

3x - 7 = 2

This is an EQUATION, because it has a left side, a right side, and an = sign separating the two.

3x - 7

This is an EXPRESSION, because there are no "sides" and no = sign

since your problem is x^4 = 81, what you have to undeo is the "to the fourth power" part.

the inverse (opposite operation) of "to the fourth power" is "to the fourth root".

  (x^4) ^ ¼   = 81 ^ ¼  

  81 = 3^4     so (3 ^ 4) ^ ¼   =   3 ^ 1   = 3

by hand: (3 ^ 4) ^ ¼   =   3 ^ (4 x ¼) = 3 ^ 1   = 3   (when you take a power to a power, multiply the exponents.)

or, do it by calculator. one way of finding the fourth root is to use ^ (1/4)

step-by-step explanation:

y/x=18

step-by-step explanation: