3x^2+5x-90=0

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Solution for 3x^2+5x-90=0 equation:


Simplifying
3x2 + 5x + -90 = 0

Reorder the terms:
-90 + 5x + 3x2 = 0

Solving
-90 + 5x + 3x2 = 0

Solving for variable 'x'.

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

Divide each side by '3'.
-30 + 1.666666667x + x2 = 0

Move the constant term to the right:

Add '30' to each side of the equation.
-30 + 1.666666667x + 30 + x2 = 0 + 30

Reorder the terms:
-30 + 30 + 1.666666667x + x2 = 0 + 30

Combine like terms: -30 + 30 = 0
0 + 1.666666667x + x2 = 0 + 30
1.666666667x + x2 = 0 + 30

Combine like terms: 0 + 30 = 30
1.666666667x + x2 = 30

The x term is 1.666666667x.  Take half its coefficient (0.8333333335).
Square it (0.6944444447) and add it to both sides.

Add '0.6944444447' to each side of the equation.
1.666666667x + 0.6944444447 + x2 = 30 + 0.6944444447

Reorder the terms:
0.6944444447 + 1.666666667x + x2 = 30 + 0.6944444447

Combine like terms: 30 + 0.6944444447 = 30.6944444447
0.6944444447 + 1.666666667x + x2 = 30.6944444447

Factor a perfect square on the left side:
(x + 0.8333333335)(x + 0.8333333335) = 30.6944444447

Calculate the square root of the right side: 5.540256713

Break this problem into two subproblems by setting 
(x + 0.8333333335) equal to 5.540256713 and -5.540256713.

Subproblem 1

x + 0.8333333335 = 5.540256713 Simplifying x + 0.8333333335 = 5.540256713 Reorder the terms: 0.8333333335 + x = 5.540256713 Solving 0.8333333335 + x = 5.540256713 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.8333333335' to each side of the equation. 0.8333333335 + -0.8333333335 + x = 5.540256713 + -0.8333333335 Combine like terms: 0.8333333335 + -0.8333333335 = 0.0000000000 0.0000000000 + x = 5.540256713 + -0.8333333335 x = 5.540256713 + -0.8333333335 Combine like terms: 5.540256713 + -0.8333333335 = 4.7069233795 x = 4.7069233795 Simplifying x = 4.7069233795

Subproblem 2

x + 0.8333333335 = -5.540256713 Simplifying x + 0.8333333335 = -5.540256713 Reorder the terms: 0.8333333335 + x = -5.540256713 Solving 0.8333333335 + x = -5.540256713 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.8333333335' to each side of the equation. 0.8333333335 + -0.8333333335 + x = -5.540256713 + -0.8333333335 Combine like terms: 0.8333333335 + -0.8333333335 = 0.0000000000 0.0000000000 + x = -5.540256713 + -0.8333333335 x = -5.540256713 + -0.8333333335 Combine like terms: -5.540256713 + -0.8333333335 = -6.3735900465 x = -6.3735900465 Simplifying x = -6.3735900465

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.7069233795, -6.3735900465}

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