(x-1)(x+2)=15

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Solution for (x-1)(x+2)=15 equation:


Simplifying
(x + -1)(x + 2) = 15

Reorder the terms:
(-1 + x)(x + 2) = 15

Reorder the terms:
(-1 + x)(2 + x) = 15

Multiply (-1 + x) * (2 + x)
(-1(2 + x) + x(2 + x)) = 15
((2 * -1 + x * -1) + x(2 + x)) = 15
((-2 + -1x) + x(2 + x)) = 15
(-2 + -1x + (2 * x + x * x)) = 15
(-2 + -1x + (2x + x2)) = 15

Combine like terms: -1x + 2x = 1x
(-2 + 1x + x2) = 15

Solving
-2 + 1x + x2 = 15

Solving for variable 'x'.

Reorder the terms:
-2 + -15 + 1x + x2 = 15 + -15

Combine like terms: -2 + -15 = -17
-17 + 1x + x2 = 15 + -15

Combine like terms: 15 + -15 = 0
-17 + 1x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '17' to each side of the equation.
-17 + 1x + 17 + x2 = 0 + 17

Reorder the terms:
-17 + 17 + 1x + x2 = 0 + 17

Combine like terms: -17 + 17 = 0
0 + 1x + x2 = 0 + 17
1x + x2 = 0 + 17

Combine like terms: 0 + 17 = 17
1x + x2 = 17

The x term is 1x.  Take half its coefficient (0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
x + 0.25 + x2 = 17 + 0.25

Reorder the terms:
0.25 + x + x2 = 17 + 0.25

Combine like terms: 17 + 0.25 = 17.25
0.25 + x + x2 = 17.25

Factor a perfect square on the left side:
(x + 0.5)(x + 0.5) = 17.25

Calculate the square root of the right side: 4.153311931

Break this problem into two subproblems by setting 
(x + 0.5) equal to 4.153311931 and -4.153311931.

Subproblem 1

x + 0.5 = 4.153311931 Simplifying x + 0.5 = 4.153311931 Reorder the terms: 0.5 + x = 4.153311931 Solving 0.5 + x = 4.153311931 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + x = 4.153311931 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + x = 4.153311931 + -0.5 x = 4.153311931 + -0.5 Combine like terms: 4.153311931 + -0.5 = 3.653311931 x = 3.653311931 Simplifying x = 3.653311931

Subproblem 2

x + 0.5 = -4.153311931 Simplifying x + 0.5 = -4.153311931 Reorder the terms: 0.5 + x = -4.153311931 Solving 0.5 + x = -4.153311931 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + x = -4.153311931 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + x = -4.153311931 + -0.5 x = -4.153311931 + -0.5 Combine like terms: -4.153311931 + -0.5 = -4.653311931 x = -4.653311931 Simplifying x = -4.653311931

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.653311931, -4.653311931}

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