4x^2-21x+9=0

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Solution for 4x^2-21x+9=0 equation:


Simplifying
4x2 + -21x + 9 = 0

Reorder the terms:
9 + -21x + 4x2 = 0

Solving
9 + -21x + 4x2 = 0

Solving for variable 'x'.

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

Divide each side by '4'.
2.25 + -5.25x + x2 = 0

Move the constant term to the right:

Add '-2.25' to each side of the equation.
2.25 + -5.25x + -2.25 + x2 = 0 + -2.25

Reorder the terms:
2.25 + -2.25 + -5.25x + x2 = 0 + -2.25

Combine like terms: 2.25 + -2.25 = 0.00
0.00 + -5.25x + x2 = 0 + -2.25
-5.25x + x2 = 0 + -2.25

Combine like terms: 0 + -2.25 = -2.25
-5.25x + x2 = -2.25

The x term is -5.25x.  Take half its coefficient (-2.625).
Square it (6.890625) and add it to both sides.

Add '6.890625' to each side of the equation.
-5.25x + 6.890625 + x2 = -2.25 + 6.890625

Reorder the terms:
6.890625 + -5.25x + x2 = -2.25 + 6.890625

Combine like terms: -2.25 + 6.890625 = 4.640625
6.890625 + -5.25x + x2 = 4.640625

Factor a perfect square on the left side:
(x + -2.625)(x + -2.625) = 4.640625

Calculate the square root of the right side: 2.154210992

Break this problem into two subproblems by setting 
(x + -2.625) equal to 2.154210992 and -2.154210992.

Subproblem 1

x + -2.625 = 2.154210992 Simplifying x + -2.625 = 2.154210992 Reorder the terms: -2.625 + x = 2.154210992 Solving -2.625 + x = 2.154210992 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.625' to each side of the equation. -2.625 + 2.625 + x = 2.154210992 + 2.625 Combine like terms: -2.625 + 2.625 = 0.000 0.000 + x = 2.154210992 + 2.625 x = 2.154210992 + 2.625 Combine like terms: 2.154210992 + 2.625 = 4.779210992 x = 4.779210992 Simplifying x = 4.779210992

Subproblem 2

x + -2.625 = -2.154210992 Simplifying x + -2.625 = -2.154210992 Reorder the terms: -2.625 + x = -2.154210992 Solving -2.625 + x = -2.154210992 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.625' to each side of the equation. -2.625 + 2.625 + x = -2.154210992 + 2.625 Combine like terms: -2.625 + 2.625 = 0.000 0.000 + x = -2.154210992 + 2.625 x = -2.154210992 + 2.625 Combine like terms: -2.154210992 + 2.625 = 0.470789008 x = 0.470789008 Simplifying x = 0.470789008

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.779210992, 0.470789008}

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