-3x(x-4)=21

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Solution for -3x(x-4)=21 equation:


Simplifying
-3x(x + -4) = 21

Reorder the terms:
-3x(-4 + x) = 21
(-4 * -3x + x * -3x) = 21
(12x + -3x2) = 21

Solving
12x + -3x2 = 21

Solving for variable 'x'.

Reorder the terms:
-21 + 12x + -3x2 = 21 + -21

Combine like terms: 21 + -21 = 0
-21 + 12x + -3x2 = 0

Factor out the Greatest Common Factor (GCF), '3'.
3(-7 + 4x + -1x2) = 0

Ignore the factor 3.

Subproblem 1

Set the factor '(-7 + 4x + -1x2)' equal to zero and attempt to solve: Simplifying -7 + 4x + -1x2 = 0 Solving -7 + 4x + -1x2 = 0 Begin completing the square. Divide all terms by -1 the coefficient of the squared term: Divide each side by '-1'. 7 + -4x + x2 = 0 Move the constant term to the right: Add '-7' to each side of the equation. 7 + -4x + -7 + x2 = 0 + -7 Reorder the terms: 7 + -7 + -4x + x2 = 0 + -7 Combine like terms: 7 + -7 = 0 0 + -4x + x2 = 0 + -7 -4x + x2 = 0 + -7 Combine like terms: 0 + -7 = -7 -4x + x2 = -7 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 = -7 + 4 Reorder the terms: 4 + -4x + x2 = -7 + 4 Combine like terms: -7 + 4 = -3 4 + -4x + x2 = -3 Factor a perfect square on the left side: (x + -2)(x + -2) = -3 Can't calculate square root of the right side. The solution to this equation could not be determined. This subproblem is being ignored because a solution could not be determined. The solution to this equation could not be determined.

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