15=-4.9x^2+20x+5

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Solution for 15=-4.9x^2+20x+5 equation:


Simplifying
15 = -4.9x2 + 20x + 5

Reorder the terms:
15 = 5 + 20x + -4.9x2

Solving
15 = 5 + 20x + -4.9x2

Solving for variable 'x'.

Combine like terms: 15 + -5 = 10
10 + -20x + 4.9x2 = 5 + 20x + -4.9x2 + -5 + -20x + 4.9x2

Reorder the terms:
10 + -20x + 4.9x2 = 5 + -5 + 20x + -20x + -4.9x2 + 4.9x2

Combine like terms: 5 + -5 = 0
10 + -20x + 4.9x2 = 0 + 20x + -20x + -4.9x2 + 4.9x2
10 + -20x + 4.9x2 = 20x + -20x + -4.9x2 + 4.9x2

Combine like terms: 20x + -20x = 0
10 + -20x + 4.9x2 = 0 + -4.9x2 + 4.9x2
10 + -20x + 4.9x2 = -4.9x2 + 4.9x2

Combine like terms: -4.9x2 + 4.9x2 = 0.0
10 + -20x + 4.9x2 = 0.0

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

Divide each side by '4.9'.
2.040816327 + -4.081632653x + x2 = 0

Move the constant term to the right:

Add '-2.040816327' to each side of the equation.
2.040816327 + -4.081632653x + -2.040816327 + x2 = 0 + -2.040816327

Reorder the terms:
2.040816327 + -2.040816327 + -4.081632653x + x2 = 0 + -2.040816327

Combine like terms: 2.040816327 + -2.040816327 = 0.000000000
0.000000000 + -4.081632653x + x2 = 0 + -2.040816327
-4.081632653x + x2 = 0 + -2.040816327

Combine like terms: 0 + -2.040816327 = -2.040816327
-4.081632653x + x2 = -2.040816327

The x term is -4.081632653x.  Take half its coefficient (-2.040816327).
Square it (4.164931281) and add it to both sides.

Add '4.164931281' to each side of the equation.
-4.081632653x + 4.164931281 + x2 = -2.040816327 + 4.164931281

Reorder the terms:
4.164931281 + -4.081632653x + x2 = -2.040816327 + 4.164931281

Combine like terms: -2.040816327 + 4.164931281 = 2.124114954
4.164931281 + -4.081632653x + x2 = 2.124114954

Factor a perfect square on the left side:
(x + -2.040816327)(x + -2.040816327) = 2.124114954

Calculate the square root of the right side: 1.457434374

Break this problem into two subproblems by setting 
(x + -2.040816327) equal to 1.457434374 and -1.457434374.

Subproblem 1

x + -2.040816327 = 1.457434374 Simplifying x + -2.040816327 = 1.457434374 Reorder the terms: -2.040816327 + x = 1.457434374 Solving -2.040816327 + x = 1.457434374 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.040816327' to each side of the equation. -2.040816327 + 2.040816327 + x = 1.457434374 + 2.040816327 Combine like terms: -2.040816327 + 2.040816327 = 0.000000000 0.000000000 + x = 1.457434374 + 2.040816327 x = 1.457434374 + 2.040816327 Combine like terms: 1.457434374 + 2.040816327 = 3.498250701 x = 3.498250701 Simplifying x = 3.498250701

Subproblem 2

x + -2.040816327 = -1.457434374 Simplifying x + -2.040816327 = -1.457434374 Reorder the terms: -2.040816327 + x = -1.457434374 Solving -2.040816327 + x = -1.457434374 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.040816327' to each side of the equation. -2.040816327 + 2.040816327 + x = -1.457434374 + 2.040816327 Combine like terms: -2.040816327 + 2.040816327 = 0.000000000 0.000000000 + x = -1.457434374 + 2.040816327 x = -1.457434374 + 2.040816327 Combine like terms: -1.457434374 + 2.040816327 = 0.583381953 x = 0.583381953 Simplifying x = 0.583381953

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.498250701, 0.583381953}

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