780=x^2+9x

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Solution for 780=x^2+9x equation:


Simplifying
780 = x2 + 9x

Reorder the terms:
780 = 9x + x2

Solving
780 = 9x + x2

Solving for variable 'x'.

Reorder the terms:
780 + -9x + -1x2 = 9x + -9x + x2 + -1x2

Combine like terms: 9x + -9x = 0
780 + -9x + -1x2 = 0 + x2 + -1x2
780 + -9x + -1x2 = x2 + -1x2

Combine like terms: x2 + -1x2 = 0
780 + -9x + -1x2 = 0

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
-780 + 9x + x2 = 0

Move the constant term to the right:

Add '780' to each side of the equation.
-780 + 9x + 780 + x2 = 0 + 780

Reorder the terms:
-780 + 780 + 9x + x2 = 0 + 780

Combine like terms: -780 + 780 = 0
0 + 9x + x2 = 0 + 780
9x + x2 = 0 + 780

Combine like terms: 0 + 780 = 780
9x + x2 = 780

The x term is 9x.  Take half its coefficient (4.5).
Square it (20.25) and add it to both sides.

Add '20.25' to each side of the equation.
9x + 20.25 + x2 = 780 + 20.25

Reorder the terms:
20.25 + 9x + x2 = 780 + 20.25

Combine like terms: 780 + 20.25 = 800.25
20.25 + 9x + x2 = 800.25

Factor a perfect square on the left side:
(x + 4.5)(x + 4.5) = 800.25

Calculate the square root of the right side: 28.28869032

Break this problem into two subproblems by setting 
(x + 4.5) equal to 28.28869032 and -28.28869032.

Subproblem 1

x + 4.5 = 28.28869032 Simplifying x + 4.5 = 28.28869032 Reorder the terms: 4.5 + x = 28.28869032 Solving 4.5 + x = 28.28869032 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + x = 28.28869032 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = 28.28869032 + -4.5 x = 28.28869032 + -4.5 Combine like terms: 28.28869032 + -4.5 = 23.78869032 x = 23.78869032 Simplifying x = 23.78869032

Subproblem 2

x + 4.5 = -28.28869032 Simplifying x + 4.5 = -28.28869032 Reorder the terms: 4.5 + x = -28.28869032 Solving 4.5 + x = -28.28869032 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + x = -28.28869032 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = -28.28869032 + -4.5 x = -28.28869032 + -4.5 Combine like terms: -28.28869032 + -4.5 = -32.78869032 x = -32.78869032 Simplifying x = -32.78869032

Solution

The solution to the problem is based on the solutions from the subproblems. x = {23.78869032, -32.78869032}

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