x(7-x)+9=-21

Solution for x(7-x)+9=-21 equation:

Simplifying
x(7 + -1x) + 9 = -21
(7 * x + -1x * x) + 9 = -21
(7x + -1x2) + 9 = -21

Reorder the terms:
9 + 7x + -1x2 = -21

Solving
9 + 7x + -1x2 = -21

Solving for variable 'x'.

Reorder the terms:
9 + 21 + 7x + -1x2 = -21 + 21

Combine like terms: 9 + 21 = 30
30 + 7x + -1x2 = -21 + 21

Combine like terms: -21 + 21 = 0
30 + 7x + -1x2 = 0

Factor a trinomial.
(10 + -1x)(3 + x) = 0

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

Simplifying
10 + -1x = 0

Solving
10 + -1x = 0

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

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

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

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

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

Simplifying
x = 10
Subproblem 2
Set the factor '(3 + x)' equal to zero and attempt to solve:

Simplifying
3 + x = 0

Solving
3 + x = 0

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

Add '-3' to each side of the equation.
3 + -3 + x = 0 + -3

Combine like terms: 3 + -3 = 0
0 + x = 0 + -3
x = 0 + -3

Combine like terms: 0 + -3 = -3
x = -3

Simplifying
x = -3
Solution
x = {10, -3}