.8x^2+3x-720=0

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Solution for .8x^2+3x-720=0 equation:


Simplifying
0.8x2 + 3x + -720 = 0

Reorder the terms:
-720 + 3x + 0.8x2 = 0

Solving
-720 + 3x + 0.8x2 = 0

Solving for variable 'x'.

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

Divide each side by '0.8'.
-900 + 3.75x + x2 = 0

Move the constant term to the right:

Add '900' to each side of the equation.
-900 + 3.75x + 900 + x2 = 0 + 900

Reorder the terms:
-900 + 900 + 3.75x + x2 = 0 + 900

Combine like terms: -900 + 900 = 0
0 + 3.75x + x2 = 0 + 900
3.75x + x2 = 0 + 900

Combine like terms: 0 + 900 = 900
3.75x + x2 = 900

The x term is 3.75x.  Take half its coefficient (1.875).
Square it (3.515625) and add it to both sides.

Add '3.515625' to each side of the equation.
3.75x + 3.515625 + x2 = 900 + 3.515625

Reorder the terms:
3.515625 + 3.75x + x2 = 900 + 3.515625

Combine like terms: 900 + 3.515625 = 903.515625
3.515625 + 3.75x + x2 = 903.515625

Factor a perfect square on the left side:
(x + 1.875)(x + 1.875) = 903.515625

Calculate the square root of the right side: 30.058536641

Break this problem into two subproblems by setting 
(x + 1.875) equal to 30.058536641 and -30.058536641.

Subproblem 1

x + 1.875 = 30.058536641 Simplifying x + 1.875 = 30.058536641 Reorder the terms: 1.875 + x = 30.058536641 Solving 1.875 + x = 30.058536641 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.875' to each side of the equation. 1.875 + -1.875 + x = 30.058536641 + -1.875 Combine like terms: 1.875 + -1.875 = 0.000 0.000 + x = 30.058536641 + -1.875 x = 30.058536641 + -1.875 Combine like terms: 30.058536641 + -1.875 = 28.183536641 x = 28.183536641 Simplifying x = 28.183536641

Subproblem 2

x + 1.875 = -30.058536641 Simplifying x + 1.875 = -30.058536641 Reorder the terms: 1.875 + x = -30.058536641 Solving 1.875 + x = -30.058536641 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.875' to each side of the equation. 1.875 + -1.875 + x = -30.058536641 + -1.875 Combine like terms: 1.875 + -1.875 = 0.000 0.000 + x = -30.058536641 + -1.875 x = -30.058536641 + -1.875 Combine like terms: -30.058536641 + -1.875 = -31.933536641 x = -31.933536641 Simplifying x = -31.933536641

Solution

The solution to the problem is based on the solutions from the subproblems. x = {28.183536641, -31.933536641}

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