r*r-4r=0

Solution for r*r-4r=0 equation:

Simplifying
r * r + -4r = 0

Multiply r * r
r2 + -4r = 0

Reorder the terms:
-4r + r2 = 0

Solving
-4r + r2 = 0

Solving for variable 'r'.

Factor out the Greatest Common Factor (GCF), 'r'.
r(-4 + r) = 0

Subproblem 1
Set the factor 'r' equal to zero and attempt to solve:

Simplifying
r = 0

Solving
r = 0

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

Simplifying
r = 0
Subproblem 2
Set the factor '(-4 + r)' equal to zero and attempt to solve:

Simplifying
-4 + r = 0

Solving
-4 + r = 0

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

Add '4' to each side of the equation.
-4 + 4 + r = 0 + 4

Combine like terms: -4 + 4 = 0
0 + r = 0 + 4
r = 0 + 4

Combine like terms: 0 + 4 = 4
r = 4

Simplifying
r = 4
Solution
r = {0, 4}