3x^2+21x=15

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Solution for 3x^2+21x=15 equation:


Simplifying
3x2 + 21x = 15

Reorder the terms:
21x + 3x2 = 15

Solving
21x + 3x2 = 15

Solving for variable 'x'.

Reorder the terms:
-15 + 21x + 3x2 = 15 + -15

Combine like terms: 15 + -15 = 0
-15 + 21x + 3x2 = 0

Factor out the Greatest Common Factor (GCF), '3'.
3(-5 + 7x + x2) = 0

Ignore the factor 3.

Subproblem 1

Set the factor '(-5 + 7x + x2)' equal to zero and attempt to solve: Simplifying -5 + 7x + x2 = 0 Solving -5 + 7x + x2 = 0 Begin completing the square. Move the constant term to the right: Add '5' to each side of the equation. -5 + 7x + 5 + x2 = 0 + 5 Reorder the terms: -5 + 5 + 7x + x2 = 0 + 5 Combine like terms: -5 + 5 = 0 0 + 7x + x2 = 0 + 5 7x + x2 = 0 + 5 Combine like terms: 0 + 5 = 5 7x + x2 = 5 The x term is 7x. Take half its coefficient (3.5). Square it (12.25) and add it to both sides. Add '12.25' to each side of the equation. 7x + 12.25 + x2 = 5 + 12.25 Reorder the terms: 12.25 + 7x + x2 = 5 + 12.25 Combine like terms: 5 + 12.25 = 17.25 12.25 + 7x + x2 = 17.25 Factor a perfect square on the left side: (x + 3.5)(x + 3.5) = 17.25 Calculate the square root of the right side: 4.153311931 Break this problem into two subproblems by setting (x + 3.5) equal to 4.153311931 and -4.153311931.

Subproblem 1

x + 3.5 = 4.153311931 Simplifying x + 3.5 = 4.153311931 Reorder the terms: 3.5 + x = 4.153311931 Solving 3.5 + x = 4.153311931 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.5' to each side of the equation. 3.5 + -3.5 + x = 4.153311931 + -3.5 Combine like terms: 3.5 + -3.5 = 0.0 0.0 + x = 4.153311931 + -3.5 x = 4.153311931 + -3.5 Combine like terms: 4.153311931 + -3.5 = 0.653311931 x = 0.653311931 Simplifying x = 0.653311931

Subproblem 2

x + 3.5 = -4.153311931 Simplifying x + 3.5 = -4.153311931 Reorder the terms: 3.5 + x = -4.153311931 Solving 3.5 + x = -4.153311931 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.5' to each side of the equation. 3.5 + -3.5 + x = -4.153311931 + -3.5 Combine like terms: 3.5 + -3.5 = 0.0 0.0 + x = -4.153311931 + -3.5 x = -4.153311931 + -3.5 Combine like terms: -4.153311931 + -3.5 = -7.653311931 x = -7.653311931 Simplifying x = -7.653311931

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.653311931, -7.653311931}

Solution

x = {0.653311931, -7.653311931}

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