0=-4.9x^2+9x+400

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Solution for 0=-4.9x^2+9x+400 equation:


Simplifying
0 = -4.9x2 + 9x + 400

Reorder the terms:
0 = 400 + 9x + -4.9x2

Solving
0 = 400 + 9x + -4.9x2

Solving for variable 'x'.

Combine like terms: 0 + -400 = -400
-400 + -9x + 4.9x2 = 400 + 9x + -4.9x2 + -400 + -9x + 4.9x2

Reorder the terms:
-400 + -9x + 4.9x2 = 400 + -400 + 9x + -9x + -4.9x2 + 4.9x2

Combine like terms: 400 + -400 = 0
-400 + -9x + 4.9x2 = 0 + 9x + -9x + -4.9x2 + 4.9x2
-400 + -9x + 4.9x2 = 9x + -9x + -4.9x2 + 4.9x2

Combine like terms: 9x + -9x = 0
-400 + -9x + 4.9x2 = 0 + -4.9x2 + 4.9x2
-400 + -9x + 4.9x2 = -4.9x2 + 4.9x2

Combine like terms: -4.9x2 + 4.9x2 = 0.0
-400 + -9x + 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'.
-81.63265306 + -1.836734694x + x2 = 0

Move the constant term to the right:

Add '81.63265306' to each side of the equation.
-81.63265306 + -1.836734694x + 81.63265306 + x2 = 0 + 81.63265306

Reorder the terms:
-81.63265306 + 81.63265306 + -1.836734694x + x2 = 0 + 81.63265306

Combine like terms: -81.63265306 + 81.63265306 = 0.00000000
0.00000000 + -1.836734694x + x2 = 0 + 81.63265306
-1.836734694x + x2 = 0 + 81.63265306

Combine like terms: 0 + 81.63265306 = 81.63265306
-1.836734694x + x2 = 81.63265306

The x term is -1.836734694x.  Take half its coefficient (-0.918367347).
Square it (0.8433985840) and add it to both sides.

Add '0.8433985840' to each side of the equation.
-1.836734694x + 0.8433985840 + x2 = 81.63265306 + 0.8433985840

Reorder the terms:
0.8433985840 + -1.836734694x + x2 = 81.63265306 + 0.8433985840

Combine like terms: 81.63265306 + 0.8433985840 = 82.476051644
0.8433985840 + -1.836734694x + x2 = 82.476051644

Factor a perfect square on the left side:
(x + -0.918367347)(x + -0.918367347) = 82.476051644

Calculate the square root of the right side: 9.081632653

Break this problem into two subproblems by setting 
(x + -0.918367347) equal to 9.081632653 and -9.081632653.

Subproblem 1

x + -0.918367347 = 9.081632653 Simplifying x + -0.918367347 = 9.081632653 Reorder the terms: -0.918367347 + x = 9.081632653 Solving -0.918367347 + x = 9.081632653 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.918367347' to each side of the equation. -0.918367347 + 0.918367347 + x = 9.081632653 + 0.918367347 Combine like terms: -0.918367347 + 0.918367347 = 0.000000000 0.000000000 + x = 9.081632653 + 0.918367347 x = 9.081632653 + 0.918367347 Combine like terms: 9.081632653 + 0.918367347 = 10 x = 10 Simplifying x = 10

Subproblem 2

x + -0.918367347 = -9.081632653 Simplifying x + -0.918367347 = -9.081632653 Reorder the terms: -0.918367347 + x = -9.081632653 Solving -0.918367347 + x = -9.081632653 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.918367347' to each side of the equation. -0.918367347 + 0.918367347 + x = -9.081632653 + 0.918367347 Combine like terms: -0.918367347 + 0.918367347 = 0.000000000 0.000000000 + x = -9.081632653 + 0.918367347 x = -9.081632653 + 0.918367347 Combine like terms: -9.081632653 + 0.918367347 = -8.163265306 x = -8.163265306 Simplifying x = -8.163265306

Solution

The solution to the problem is based on the solutions from the subproblems. x = {10, -8.163265306}

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