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Simplifying
x2 + x + -3.75 = 0

Reorder the terms:
-3.75 + x + x2 = 0

Solving
-3.75 + x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '3.75' to each side of the equation.
-3.75 + x + 3.75 + x2 = 0 + 3.75

Reorder the terms:
-3.75 + 3.75 + x + x2 = 0 + 3.75

Combine like terms: -3.75 + 3.75 = 0.00
0.00 + x + x2 = 0 + 3.75
x + x2 = 0 + 3.75

Combine like terms: 0 + 3.75 = 3.75
x + x2 = 3.75

The x term is x.  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 = 3.75 + 0.25

Reorder the terms:
0.25 + x + x2 = 3.75 + 0.25

Combine like terms: 3.75 + 0.25 = 4
0.25 + x + x2 = 4

Factor a perfect square on the left side:
(x + 0.5)(x + 0.5) = 4

Calculate the square root of the right side: 2

Break this problem into two subproblems by setting 
(x + 0.5) equal to 2 and -2.

Subproblem 1

x + 0.5 = 2 Simplifying x + 0.5 = 2 Reorder the terms: 0.5 + x = 2 Solving 0.5 + x = 2 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 = 2 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + x = 2 + -0.5 x = 2 + -0.5 Combine like terms: 2 + -0.5 = 1.5 x = 1.5 Simplifying x = 1.5

Subproblem 2

x + 0.5 = -2 Simplifying x + 0.5 = -2 Reorder the terms: 0.5 + x = -2 Solving 0.5 + x = -2 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 = -2 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + x = -2 + -0.5 x = -2 + -0.5 Combine like terms: -2 + -0.5 = -2.5 x = -2.5 Simplifying x = -2.5

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.5, -2.5}
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