(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 = 3.830951895 x = 3.830951895 Simplifying x = 3.830951895

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 = -7.830951895 x = -7.830951895 Simplifying x = -7.830951895

Solution

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

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