45=(7x^2)+21x

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Solution for 45=(7x^2)+21x equation:


Simplifying
45 = (7x2) + 21x

Reorder the terms:
45 = 21x + (7x2)

Solving
45 = 21x + (7x2)

Solving for variable 'x'.

Reorder the terms:
45 + -21x + (-7x2) = 21x + -21x + (7x2) + (-7x2)

Combine like terms: 21x + -21x = 0
45 + -21x + (-7x2) = 0 + (7x2) + (-7x2)
45 + -21x + (-7x2) = (7x2) + (-7x2)

Combine like terms: (7x2) + (-7x2) = 0
45 + -21x + (-7x2) = 0

Begin completing the square.  Divide all terms by
-7 the coefficient of the squared term: 

Divide each side by '-7'.
-6.428571429 + 3x + x2 = 0

Move the constant term to the right:

Add '6.428571429' to each side of the equation.
-6.428571429 + 3x + 6.428571429 + x2 = 0 + 6.428571429

Reorder the terms:
-6.428571429 + 6.428571429 + 3x + x2 = 0 + 6.428571429

Combine like terms: -6.428571429 + 6.428571429 = 0.000000000
0.000000000 + 3x + x2 = 0 + 6.428571429
3x + x2 = 0 + 6.428571429

Combine like terms: 0 + 6.428571429 = 6.428571429
3x + x2 = 6.428571429

The x term is 3x.  Take half its coefficient (1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
3x + 2.25 + x2 = 6.428571429 + 2.25

Reorder the terms:
2.25 + 3x + x2 = 6.428571429 + 2.25

Combine like terms: 6.428571429 + 2.25 = 8.678571429
2.25 + 3x + x2 = 8.678571429

Factor a perfect square on the left side:
((x) + 1.5)((x) + 1.5) = 8.678571429

Calculate the square root of the right side: 2.945941518

Break this problem into two subproblems by setting 
((x) + 1.5) equal to 2.945941518 and -2.945941518.

Subproblem 1

(x) + 1.5 = 2.945941518 Simplifying (x) + 1.5 = 2.945941518 x + 1.5 = 2.945941518 Reorder the terms: 1.5 + x = 2.945941518 Solving 1.5 + x = 2.945941518 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.5' to each side of the equation. 1.5 + -1.5 + x = 2.945941518 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = 2.945941518 + -1.5 x = 2.945941518 + -1.5 Combine like terms: 2.945941518 + -1.5 = 1.445941518 x = 1.445941518 Simplifying x = 1.445941518

Subproblem 2

(x) + 1.5 = -2.945941518 Simplifying (x) + 1.5 = -2.945941518 x + 1.5 = -2.945941518 Reorder the terms: 1.5 + x = -2.945941518 Solving 1.5 + x = -2.945941518 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.5' to each side of the equation. 1.5 + -1.5 + x = -2.945941518 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = -2.945941518 + -1.5 x = -2.945941518 + -1.5 Combine like terms: -2.945941518 + -1.5 = -4.445941518 x = -4.445941518 Simplifying x = -4.445941518

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.445941518, -4.445941518}

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