(x+7)(x-3)=90

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Solution for (x+7)(x-3)=90 equation:


Simplifying
(x + 7)(x + -3) = 90

Reorder the terms:
(7 + x)(x + -3) = 90

Reorder the terms:
(7 + x)(-3 + x) = 90

Multiply (7 + x) * (-3 + x)
(7(-3 + x) + x(-3 + x)) = 90
((-3 * 7 + x * 7) + x(-3 + x)) = 90
((-21 + 7x) + x(-3 + x)) = 90
(-21 + 7x + (-3 * x + x * x)) = 90
(-21 + 7x + (-3x + x2)) = 90

Combine like terms: 7x + -3x = 4x
(-21 + 4x + x2) = 90

Solving
-21 + 4x + x2 = 90

Solving for variable 'x'.

Reorder the terms:
-21 + -90 + 4x + x2 = 90 + -90

Combine like terms: -21 + -90 = -111
-111 + 4x + x2 = 90 + -90

Combine like terms: 90 + -90 = 0
-111 + 4x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '111' to each side of the equation.
-111 + 4x + 111 + x2 = 0 + 111

Reorder the terms:
-111 + 111 + 4x + x2 = 0 + 111

Combine like terms: -111 + 111 = 0
0 + 4x + x2 = 0 + 111
4x + x2 = 0 + 111

Combine like terms: 0 + 111 = 111
4x + x2 = 111

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 = 111 + 4

Reorder the terms:
4 + 4x + x2 = 111 + 4

Combine like terms: 111 + 4 = 115
4 + 4x + x2 = 115

Factor a perfect square on the left side:
(x + 2)(x + 2) = 115

Calculate the square root of the right side: 10.723805295

Break this problem into two subproblems by setting 
(x + 2) equal to 10.723805295 and -10.723805295.

Subproblem 1

x + 2 = 10.723805295 Simplifying x + 2 = 10.723805295 Reorder the terms: 2 + x = 10.723805295 Solving 2 + x = 10.723805295 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 = 10.723805295 + -2 Combine like terms: 2 + -2 = 0 0 + x = 10.723805295 + -2 x = 10.723805295 + -2 Combine like terms: 10.723805295 + -2 = 8.723805295 x = 8.723805295 Simplifying x = 8.723805295

Subproblem 2

x + 2 = -10.723805295 Simplifying x + 2 = -10.723805295 Reorder the terms: 2 + x = -10.723805295 Solving 2 + x = -10.723805295 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 = -10.723805295 + -2 Combine like terms: 2 + -2 = 0 0 + x = -10.723805295 + -2 x = -10.723805295 + -2 Combine like terms: -10.723805295 + -2 = -12.723805295 x = -12.723805295 Simplifying x = -12.723805295

Solution

The solution to the problem is based on the solutions from the subproblems. x = {8.723805295, -12.723805295}

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