(x+3)(x-7)=9

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Solution for (x+3)(x-7)=9 equation:


Simplifying
(x + 3)(x + -7) = 9

Reorder the terms:
(3 + x)(x + -7) = 9

Reorder the terms:
(3 + x)(-7 + x) = 9

Multiply (3 + x) * (-7 + x)
(3(-7 + x) + x(-7 + x)) = 9
((-7 * 3 + x * 3) + x(-7 + x)) = 9
((-21 + 3x) + x(-7 + x)) = 9
(-21 + 3x + (-7 * x + x * x)) = 9
(-21 + 3x + (-7x + x2)) = 9

Combine like terms: 3x + -7x = -4x
(-21 + -4x + x2) = 9

Solving
-21 + -4x + x2 = 9

Solving for variable 'x'.

Reorder the terms:
-21 + -9 + -4x + x2 = 9 + -9

Combine like terms: -21 + -9 = -30
-30 + -4x + x2 = 9 + -9

Combine like terms: 9 + -9 = 0
-30 + -4x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '30' to each side of the equation.
-30 + -4x + 30 + x2 = 0 + 30

Reorder the terms:
-30 + 30 + -4x + x2 = 0 + 30

Combine like terms: -30 + 30 = 0
0 + -4x + x2 = 0 + 30
-4x + x2 = 0 + 30

Combine like terms: 0 + 30 = 30
-4x + x2 = 30

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 = 30 + 4

Reorder the terms:
4 + -4x + x2 = 30 + 4

Combine like terms: 30 + 4 = 34
4 + -4x + x2 = 34

Factor a perfect square on the left side:
(x + -2)(x + -2) = 34

Calculate the square root of the right side: 5.830951895

Break this problem into two subproblems by setting 
(x + -2) equal to 5.830951895 and -5.830951895.

Subproblem 1

x + -2 = 5.830951895 Simplifying x + -2 = 5.830951895 Reorder the terms: -2 + x = 5.830951895 Solving -2 + x = 5.830951895 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + x = 5.830951895 + 2 Combine like terms: -2 + 2 = 0 0 + x = 5.830951895 + 2 x = 5.830951895 + 2 Combine like terms: 5.830951895 + 2 = 7.830951895 x = 7.830951895 Simplifying x = 7.830951895

Subproblem 2

x + -2 = -5.830951895 Simplifying x + -2 = -5.830951895 Reorder the terms: -2 + x = -5.830951895 Solving -2 + x = -5.830951895 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + x = -5.830951895 + 2 Combine like terms: -2 + 2 = 0 0 + x = -5.830951895 + 2 x = -5.830951895 + 2 Combine like terms: -5.830951895 + 2 = -3.830951895 x = -3.830951895 Simplifying x = -3.830951895

Solution

The solution to the problem is based on the solutions from the subproblems. x = {7.830951895, -3.830951895}

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