x^2-x=3x+21

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Solution for x^2-x=3x+21 equation:


Simplifying
x2 + -1x = 3x + 21

Reorder the terms:
-1x + x2 = 3x + 21

Reorder the terms:
-1x + x2 = 21 + 3x

Solving
-1x + x2 = 21 + 3x

Solving for variable 'x'.

Reorder the terms:
-21 + -1x + -3x + x2 = 21 + 3x + -21 + -3x

Combine like terms: -1x + -3x = -4x
-21 + -4x + x2 = 21 + 3x + -21 + -3x

Reorder the terms:
-21 + -4x + x2 = 21 + -21 + 3x + -3x

Combine like terms: 21 + -21 = 0
-21 + -4x + x2 = 0 + 3x + -3x
-21 + -4x + x2 = 3x + -3x

Combine like terms: 3x + -3x = 0
-21 + -4x + x2 = 0

Factor a trinomial.
(-3 + -1x)(7 + -1x) = 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 + -1x)' equal to zero and attempt to solve: Simplifying 7 + -1x = 0 Solving 7 + -1x = 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 + -1x = 0 + -7 Combine like terms: 7 + -7 = 0 0 + -1x = 0 + -7 -1x = 0 + -7 Combine like terms: 0 + -7 = -7 -1x = -7 Divide each side by '-1'. x = 7 Simplifying x = 7

Solution

x = {-3, 7}

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