x=0.25*((1.1212121212*(15-1.75*x)-2.5)*(0.85*(15-1.75*x)-2.5))

Solution for x=0.25*((1.1212121212*(15-1.75*x)-2.5)*(0.85*(15-1.75*x)-2.5)) equation:

Simplifying
x = 0.25((1.1212121212(15 + -1.75x) + -2.5)(0.85(15 + -1.75x) + -2.5))
x = 0.25(((15 * 1.1212121212 + -1.75x * 1.1212121212) + -2.5)(0.85(15 + -1.75x) + -2.5))
x = 0.25(((16.81818182 + -1.962121212x) + -2.5)(0.85(15 + -1.75x) + -2.5))

Reorder the terms:
x = 0.25((16.81818182 + -2.5 + -1.962121212x)(0.85(15 + -1.75x) + -2.5))

Combine like terms: 16.81818182 + -2.5 = 14.31818182
x = 0.25((14.31818182 + -1.962121212x)(0.85(15 + -1.75x) + -2.5))
x = 0.25((14.31818182 + -1.962121212x)((15 * 0.85 + -1.75x * 0.85) + -2.5))
x = 0.25((14.31818182 + -1.962121212x)((12.75 + -1.4875x) + -2.5))

Reorder the terms:
x = 0.25((14.31818182 + -1.962121212x)(12.75 + -2.5 + -1.4875x))

Combine like terms: 12.75 + -2.5 = 10.25
x = 0.25((14.31818182 + -1.962121212x)(10.25 + -1.4875x))

Multiply (14.31818182 + -1.962121212x) * (10.25 + -1.4875x)
x = 0.25((14.31818182(10.25 + -1.4875x) + -1.962121212x * (10.25 + -1.4875x)))
x = 0.25(((10.25 * 14.31818182 + -1.4875x * 14.31818182) + -1.962121212x * (10.25 + -1.4875x)))
x = 0.25(((146.7613637 + -21.29829546x) + -1.962121212x * (10.25 + -1.4875x)))
x = 0.25((146.7613637 + -21.29829546x + (10.25 * -1.962121212x + -1.4875x * -1.962121212x)))
x = 0.25((146.7613637 + -21.29829546x + (-20.11174242x + 2.918655303x2)))

Combine like terms: -21.29829546x + -20.11174242x = -41.41003788x
x = 0.25((146.7613637 + -41.41003788x + 2.918655303x2))
x = (146.7613637 * 0.25 + -41.41003788x * 0.25 + 2.918655303x2 * 0.25)
x = (36.69034093 + -10.35250947x + 0.7296638258x2)

Solving
x = 36.69034093 + -10.35250947x + 0.7296638258x2

Solving for variable 'x'.

Reorder the terms:
-36.69034093 + x + 10.35250947x + -0.7296638258x2 = 36.69034093 + -10.35250947x + 0.7296638258x2 + -36.69034093 + 10.35250947x + -0.7296638258x2

Combine like terms: x + 10.35250947x = 11.35250947x
-36.69034093 + 11.35250947x + -0.7296638258x2 = 36.69034093 + -10.35250947x + 0.7296638258x2 + -36.69034093 + 10.35250947x + -0.7296638258x2

Reorder the terms:
-36.69034093 + 11.35250947x + -0.7296638258x2 = 36.69034093 + -36.69034093 + -10.35250947x + 10.35250947x + 0.7296638258x2 + -0.7296638258x2

Combine like terms: 36.69034093 + -36.69034093 = 0.00000000
-36.69034093 + 11.35250947x + -0.7296638258x2 = 0.00000000 + -10.35250947x + 10.35250947x + 0.7296638258x2 + -0.7296638258x2
-36.69034093 + 11.35250947x + -0.7296638258x2 = -10.35250947x + 10.35250947x + 0.7296638258x2 + -0.7296638258x2

Combine like terms: -10.35250947x + 10.35250947x = 0.00000000
-36.69034093 + 11.35250947x + -0.7296638258x2 = 0.00000000 + 0.7296638258x2 + -0.7296638258x2
-36.69034093 + 11.35250947x + -0.7296638258x2 = 0.7296638258x2 + -0.7296638258x2

Combine like terms: 0.7296638258x2 + -0.7296638258x2 = 0.0000000000
-36.69034093 + 11.35250947x + -0.7296638258x2 = 0.0000000000

Begin completing the square.  Divide all terms by
-0.7296638258 the coefficient of the squared term: 

Divide each side by '-0.7296638258'.
50.28389737 + -15.55854774x + x2 = 0

Move the constant term to the right:

Add '-50.28389737' to each side of the equation.
50.28389737 + -15.55854774x + -50.28389737 + x2 = 0 + -50.28389737

Reorder the terms:
50.28389737 + -50.28389737 + -15.55854774x + x2 = 0 + -50.28389737

Combine like terms: 50.28389737 + -50.28389737 = 0.00000000
0.00000000 + -15.55854774x + x2 = 0 + -50.28389737
-15.55854774x + x2 = 0 + -50.28389737

Combine like terms: 0 + -50.28389737 = -50.28389737
-15.55854774x + x2 = -50.28389737

The x term is -15.55854774x.  Take half its coefficient (-7.77927387).
Square it (60.51710194) and add it to both sides.

Add '60.51710194' to each side of the equation.
-15.55854774x + 60.51710194 + x2 = -50.28389737 + 60.51710194

Reorder the terms:
60.51710194 + -15.55854774x + x2 = -50.28389737 + 60.51710194

Combine like terms: -50.28389737 + 60.51710194 = 10.23320457
60.51710194 + -15.55854774x + x2 = 10.23320457

Factor a perfect square on the left side:
(x + -7.77927387)(x + -7.77927387) = 10.23320457

Calculate the square root of the right side: 3.198938038

Break this problem into two subproblems by setting 
(x + -7.77927387) equal to 3.198938038 and -3.198938038.

Subproblem 1
x + -7.77927387 = 3.198938038

Simplifying
x + -7.77927387 = 3.198938038

Reorder the terms:
-7.77927387 + x = 3.198938038

Solving
-7.77927387 + x = 3.198938038

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '7.77927387' to each side of the equation.
-7.77927387 + 7.77927387 + x = 3.198938038 + 7.77927387

Combine like terms: -7.77927387 + 7.77927387 = 0.00000000
0.00000000 + x = 3.198938038 + 7.77927387
x = 3.198938038 + 7.77927387

Combine like terms: 3.198938038 + 7.77927387 = 10.978211908
x = 10.978211908

Simplifying
x = 10.978211908

Subproblem 2
x + -7.77927387 = -3.198938038

Simplifying
x + -7.77927387 = -3.198938038

Reorder the terms:
-7.77927387 + x = -3.198938038

Solving
-7.77927387 + x = -3.198938038

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '7.77927387' to each side of the equation.
-7.77927387 + 7.77927387 + x = -3.198938038 + 7.77927387

Combine like terms: -7.77927387 + 7.77927387 = 0.00000000
0.00000000 + x = -3.198938038 + 7.77927387
x = -3.198938038 + 7.77927387

Combine like terms: -3.198938038 + 7.77927387 = 4.580335832
x = 4.580335832

Simplifying
x = 4.580335832

Solution
The solution to the problem is based on the solutions
from the subproblems.
x = {10.978211908, 4.580335832}