6+(4-x)*x=21

Solution for 6+(4-x)*x=21 equation:

Simplifying
6 + (4 + -1x) * x = 21

Reorder the terms for easier multiplication:
6 + x(4 + -1x) = 21
6 + (4 * x + -1x * x) = 21
6 + (4x + -1x2) = 21

Solving
6 + 4x + -1x2 = 21

Solving for variable 'x'.

Reorder the terms:
6 + -21 + 4x + -1x2 = 21 + -21

Combine like terms: 6 + -21 = -15
-15 + 4x + -1x2 = 21 + -21

Combine like terms: 21 + -21 = 0
-15 + 4x + -1x2 = 0

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
15 + -4x + x2 = 0

Move the constant term to the right:

Add '-15' to each side of the equation.
15 + -4x + -15 + x2 = 0 + -15

Reorder the terms:
15 + -15 + -4x + x2 = 0 + -15

Combine like terms: 15 + -15 = 0
0 + -4x + x2 = 0 + -15
-4x + x2 = 0 + -15

Combine like terms: 0 + -15 = -15
-4x + x2 = -15

The x term is -4x.  Take half its coefficient (-2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
-4x + 4 + x2 = -15 + 4

Reorder the terms:
4 + -4x + x2 = -15 + 4

Combine like terms: -15 + 4 = -11
4 + -4x + x2 = -11

Factor a perfect square on the left side:
(x + -2)(x + -2) = -11

Can't calculate square root of the right side.

The solution to this equation could not be determined.