.81=b^4

Solution for .81=b^4 equation:

Simplifying
0.81 = b4

Solving
0.81 = b4

Solving for variable 'b'.

Move all terms containing b to the left, all other terms to the right.

Add '-1b4' to each side of the equation.
0.81 + -1b4 = b4 + -1b4

Combine like terms: b4 + -1b4 = 0
0.81 + -1b4 = 0

Add '-0.81' to each side of the equation.
0.81 + -0.81 + -1b4 = 0 + -0.81

Combine like terms: 0.81 + -0.81 = 0.00
0.00 + -1b4 = 0 + -0.81
-1b4 = 0 + -0.81

Combine like terms: 0 + -0.81 = -0.81
-1b4 = -0.81

Divide each side by '-1'.
b4 = 0.81

Simplifying
b4 = 0.81

Reorder the terms:
-0.81 + b4 = 0.81 + -0.81

Combine like terms: 0.81 + -0.81 = 0.00
-0.81 + b4 = 0.00

Factor a difference between two squares.
(0.9 + b2)(-0.9 + b2) = 0.00

Subproblem 1
Set the factor '(0.9 + b2)' equal to zero and attempt to solve:

Simplifying
0.9 + b2 = 0

Solving
0.9 + b2 = 0

Move all terms containing b to the left, all other terms to the right.

Add '-0.9' to each side of the equation.
0.9 + -0.9 + b2 = 0 + -0.9

Combine like terms: 0.9 + -0.9 = 0.0
0.0 + b2 = 0 + -0.9
b2 = 0 + -0.9

Combine like terms: 0 + -0.9 = -0.9
b2 = -0.9

Simplifying
b2 = -0.9

The solution to this equation could not be determined.

This subproblem is being ignored because a solution could not be determined.
Subproblem 2
Set the factor '(-0.9 + b2)' equal to zero and attempt to solve:

Simplifying
-0.9 + b2 = 0

Solving
-0.9 + b2 = 0

Move all terms containing b to the left, all other terms to the right.

Add '0.9' to each side of the equation.
-0.9 + 0.9 + b2 = 0 + 0.9

Combine like terms: -0.9 + 0.9 = 0.0
0.0 + b2 = 0 + 0.9
b2 = 0 + 0.9

Combine like terms: 0 + 0.9 = 0.9
b2 = 0.9

Simplifying
b2 = 0.9

Take the square root of each side:
b = {-0.948683298, 0.948683298}
Solution
b = {-0.948683298, 0.948683298}