10=c(c-9)

Solution for 10=c(c-9) equation:

Simplifying
10 = c(c + -9)

Reorder the terms:
10 = c(-9 + c)
10 = (-9 * c + c * c)
10 = (-9c + c2)

Solving
10 = -9c + c2

Solving for variable 'c'.

Reorder the terms:
10 + 9c + -1c2 = -9c + 9c + c2 + -1c2

Combine like terms: -9c + 9c = 0
10 + 9c + -1c2 = 0 + c2 + -1c2
10 + 9c + -1c2 = c2 + -1c2

Combine like terms: c2 + -1c2 = 0
10 + 9c + -1c2 = 0

Factor a trinomial.
(10 + -1c)(1 + c) = 0

Subproblem 1
Set the factor '(10 + -1c)' equal to zero and attempt to solve:

Simplifying
10 + -1c = 0

Solving
10 + -1c = 0

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

Add '-10' to each side of the equation.
10 + -10 + -1c = 0 + -10

Combine like terms: 10 + -10 = 0
0 + -1c = 0 + -10
-1c = 0 + -10

Combine like terms: 0 + -10 = -10
-1c = -10

Divide each side by '-1'.
c = 10

Simplifying
c = 10
Subproblem 2
Set the factor '(1 + c)' equal to zero and attempt to solve:

Simplifying
1 + c = 0

Solving
1 + c = 0

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

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

Combine like terms: 1 + -1 = 0
0 + c = 0 + -1
c = 0 + -1

Combine like terms: 0 + -1 = -1
c = -1

Simplifying
c = -1
Solution
c = {10, -1}