4x(x+5)=-21

Solution for 4x(x+5)=-21 equation:

Simplifying
4x(x + 5) = -21

Reorder the terms:
4x(5 + x) = -21
(5 * 4x + x * 4x) = -21
(20x + 4x2) = -21

Solving
20x + 4x2 = -21

Solving for variable 'x'.

Reorder the terms:
21 + 20x + 4x2 = -21 + 21

Combine like terms: -21 + 21 = 0
21 + 20x + 4x2 = 0

Factor a trinomial.
(7 + 2x)(3 + 2x) = 0

Subproblem 1
Set the factor '(7 + 2x)' equal to zero and attempt to solve:

Simplifying
7 + 2x = 0

Solving
7 + 2x = 0

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

Add '-7' to each side of the equation.
7 + -7 + 2x = 0 + -7

Combine like terms: 7 + -7 = 0
0 + 2x = 0 + -7
2x = 0 + -7

Combine like terms: 0 + -7 = -7
2x = -7

Divide each side by '2'.
x = -3.5

Simplifying
x = -3.5
Subproblem 2
Set the factor '(3 + 2x)' equal to zero and attempt to solve:

Simplifying
3 + 2x = 0

Solving
3 + 2x = 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 + 2x = 0 + -3

Combine like terms: 3 + -3 = 0
0 + 2x = 0 + -3
2x = 0 + -3

Combine like terms: 0 + -3 = -3
2x = -3

Divide each side by '2'.
x = -1.5

Simplifying
x = -1.5
Solution
x = {-3.5, -1.5}