x^2+10x+21=784

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Solution for x^2+10x+21=784 equation:


Simplifying
x2 + 10x + 21 = 784

Reorder the terms:
21 + 10x + x2 = 784

Solving
21 + 10x + x2 = 784

Solving for variable 'x'.

Reorder the terms:
21 + -784 + 10x + x2 = 784 + -784

Combine like terms: 21 + -784 = -763
-763 + 10x + x2 = 784 + -784

Combine like terms: 784 + -784 = 0
-763 + 10x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '763' to each side of the equation.
-763 + 10x + 763 + x2 = 0 + 763

Reorder the terms:
-763 + 763 + 10x + x2 = 0 + 763

Combine like terms: -763 + 763 = 0
0 + 10x + x2 = 0 + 763
10x + x2 = 0 + 763

Combine like terms: 0 + 763 = 763
10x + x2 = 763

The x term is 10x.  Take half its coefficient (5).
Square it (25) and add it to both sides.

Add '25' to each side of the equation.
10x + 25 + x2 = 763 + 25

Reorder the terms:
25 + 10x + x2 = 763 + 25

Combine like terms: 763 + 25 = 788
25 + 10x + x2 = 788

Factor a perfect square on the left side:
(x + 5)(x + 5) = 788

Calculate the square root of the right side: 28.071337695

Break this problem into two subproblems by setting 
(x + 5) equal to 28.071337695 and -28.071337695.

Subproblem 1

x + 5 = 28.071337695 Simplifying x + 5 = 28.071337695 Reorder the terms: 5 + x = 28.071337695 Solving 5 + x = 28.071337695 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-5' to each side of the equation. 5 + -5 + x = 28.071337695 + -5 Combine like terms: 5 + -5 = 0 0 + x = 28.071337695 + -5 x = 28.071337695 + -5 Combine like terms: 28.071337695 + -5 = 23.071337695 x = 23.071337695 Simplifying x = 23.071337695

Subproblem 2

x + 5 = -28.071337695 Simplifying x + 5 = -28.071337695 Reorder the terms: 5 + x = -28.071337695 Solving 5 + x = -28.071337695 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-5' to each side of the equation. 5 + -5 + x = -28.071337695 + -5 Combine like terms: 5 + -5 = 0 0 + x = -28.071337695 + -5 x = -28.071337695 + -5 Combine like terms: -28.071337695 + -5 = -33.071337695 x = -33.071337695 Simplifying x = -33.071337695

Solution

The solution to the problem is based on the solutions from the subproblems. x = {23.071337695, -33.071337695}

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