-5x^2-21x+30=0

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Solution for -5x^2-21x+30=0 equation:


Simplifying
-5x2 + -21x + 30 = 0

Reorder the terms:
30 + -21x + -5x2 = 0

Solving
30 + -21x + -5x2 = 0

Solving for variable 'x'.

Begin completing the square.  Divide all terms by
-5 the coefficient of the squared term: 

Divide each side by '-5'.
-6 + 4.2x + x2 = 0

Move the constant term to the right:

Add '6' to each side of the equation.
-6 + 4.2x + 6 + x2 = 0 + 6

Reorder the terms:
-6 + 6 + 4.2x + x2 = 0 + 6

Combine like terms: -6 + 6 = 0
0 + 4.2x + x2 = 0 + 6
4.2x + x2 = 0 + 6

Combine like terms: 0 + 6 = 6
4.2x + x2 = 6

The x term is 4.2x.  Take half its coefficient (2.1).
Square it (4.41) and add it to both sides.

Add '4.41' to each side of the equation.
4.2x + 4.41 + x2 = 6 + 4.41

Reorder the terms:
4.41 + 4.2x + x2 = 6 + 4.41

Combine like terms: 6 + 4.41 = 10.41
4.41 + 4.2x + x2 = 10.41

Factor a perfect square on the left side:
(x + 2.1)(x + 2.1) = 10.41

Calculate the square root of the right side: 3.226453161

Break this problem into two subproblems by setting 
(x + 2.1) equal to 3.226453161 and -3.226453161.

Subproblem 1

x + 2.1 = 3.226453161 Simplifying x + 2.1 = 3.226453161 Reorder the terms: 2.1 + x = 3.226453161 Solving 2.1 + x = 3.226453161 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.1' to each side of the equation. 2.1 + -2.1 + x = 3.226453161 + -2.1 Combine like terms: 2.1 + -2.1 = 0.0 0.0 + x = 3.226453161 + -2.1 x = 3.226453161 + -2.1 Combine like terms: 3.226453161 + -2.1 = 1.126453161 x = 1.126453161 Simplifying x = 1.126453161

Subproblem 2

x + 2.1 = -3.226453161 Simplifying x + 2.1 = -3.226453161 Reorder the terms: 2.1 + x = -3.226453161 Solving 2.1 + x = -3.226453161 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.1' to each side of the equation. 2.1 + -2.1 + x = -3.226453161 + -2.1 Combine like terms: 2.1 + -2.1 = 0.0 0.0 + x = -3.226453161 + -2.1 x = -3.226453161 + -2.1 Combine like terms: -3.226453161 + -2.1 = -5.326453161 x = -5.326453161 Simplifying x = -5.326453161

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.126453161, -5.326453161}

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