21=x^2+4x

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Solution for 21=x^2+4x equation:


Simplifying
21 = x2 + 4x

Reorder the terms:
21 = 4x + x2

Solving
21 = 4x + x2

Solving for variable 'x'.

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

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

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

Factor a trinomial.
(3 + -1x)(7 + x) = 0

Subproblem 1

Set the factor '(3 + -1x)' equal to zero and attempt to solve: Simplifying 3 + -1x = 0 Solving 3 + -1x = 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 + -1x = 0 + -3 Combine like terms: 3 + -3 = 0 0 + -1x = 0 + -3 -1x = 0 + -3 Combine like terms: 0 + -3 = -3 -1x = -3 Divide each side by '-1'. x = 3 Simplifying x = 3

Subproblem 2

Set the factor '(7 + x)' equal to zero and attempt to solve: Simplifying 7 + x = 0 Solving 7 + x = 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 + x = 0 + -7 Combine like terms: 7 + -7 = 0 0 + x = 0 + -7 x = 0 + -7 Combine like terms: 0 + -7 = -7 x = -7 Simplifying x = -7

Solution

x = {3, -7}

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