21x^2-121x=40

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Solution for 21x^2-121x=40 equation:


Simplifying
21x2 + -121x = 40

Reorder the terms:
-121x + 21x2 = 40

Solving
-121x + 21x2 = 40

Solving for variable 'x'.

Reorder the terms:
-40 + -121x + 21x2 = 40 + -40

Combine like terms: 40 + -40 = 0
-40 + -121x + 21x2 = 0

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

Divide each side by '21'.
-1.904761905 + -5.761904762x + x2 = 0

Move the constant term to the right:

Add '1.904761905' to each side of the equation.
-1.904761905 + -5.761904762x + 1.904761905 + x2 = 0 + 1.904761905

Reorder the terms:
-1.904761905 + 1.904761905 + -5.761904762x + x2 = 0 + 1.904761905

Combine like terms: -1.904761905 + 1.904761905 = 0.000000000
0.000000000 + -5.761904762x + x2 = 0 + 1.904761905
-5.761904762x + x2 = 0 + 1.904761905

Combine like terms: 0 + 1.904761905 = 1.904761905
-5.761904762x + x2 = 1.904761905

The x term is -5.761904762x.  Take half its coefficient (-2.880952381).
Square it (8.299886622) and add it to both sides.

Add '8.299886622' to each side of the equation.
-5.761904762x + 8.299886622 + x2 = 1.904761905 + 8.299886622

Reorder the terms:
8.299886622 + -5.761904762x + x2 = 1.904761905 + 8.299886622

Combine like terms: 1.904761905 + 8.299886622 = 10.204648527
8.299886622 + -5.761904762x + x2 = 10.204648527

Factor a perfect square on the left side:
(x + -2.880952381)(x + -2.880952381) = 10.204648527

Calculate the square root of the right side: 3.194471557

Break this problem into two subproblems by setting 
(x + -2.880952381) equal to 3.194471557 and -3.194471557.

Subproblem 1

x + -2.880952381 = 3.194471557 Simplifying x + -2.880952381 = 3.194471557 Reorder the terms: -2.880952381 + x = 3.194471557 Solving -2.880952381 + x = 3.194471557 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.880952381' to each side of the equation. -2.880952381 + 2.880952381 + x = 3.194471557 + 2.880952381 Combine like terms: -2.880952381 + 2.880952381 = 0.000000000 0.000000000 + x = 3.194471557 + 2.880952381 x = 3.194471557 + 2.880952381 Combine like terms: 3.194471557 + 2.880952381 = 6.075423938 x = 6.075423938 Simplifying x = 6.075423938

Subproblem 2

x + -2.880952381 = -3.194471557 Simplifying x + -2.880952381 = -3.194471557 Reorder the terms: -2.880952381 + x = -3.194471557 Solving -2.880952381 + x = -3.194471557 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.880952381' to each side of the equation. -2.880952381 + 2.880952381 + x = -3.194471557 + 2.880952381 Combine like terms: -2.880952381 + 2.880952381 = 0.000000000 0.000000000 + x = -3.194471557 + 2.880952381 x = -3.194471557 + 2.880952381 Combine like terms: -3.194471557 + 2.880952381 = -0.313519176 x = -0.313519176 Simplifying x = -0.313519176

Solution

The solution to the problem is based on the solutions from the subproblems. x = {6.075423938, -0.313519176}

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