2x^2-15x-42=0

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Solution for 2x^2-15x-42=0 equation:


Simplifying
2x2 + -15x + -42 = 0

Reorder the terms:
-42 + -15x + 2x2 = 0

Solving
-42 + -15x + 2x2 = 0

Solving for variable 'x'.

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

Divide each side by '2'.
-21 + -7.5x + x2 = 0

Move the constant term to the right:

Add '21' to each side of the equation.
-21 + -7.5x + 21 + x2 = 0 + 21

Reorder the terms:
-21 + 21 + -7.5x + x2 = 0 + 21

Combine like terms: -21 + 21 = 0
0 + -7.5x + x2 = 0 + 21
-7.5x + x2 = 0 + 21

Combine like terms: 0 + 21 = 21
-7.5x + x2 = 21

The x term is -7.5x.  Take half its coefficient (-3.75).
Square it (14.0625) and add it to both sides.

Add '14.0625' to each side of the equation.
-7.5x + 14.0625 + x2 = 21 + 14.0625

Reorder the terms:
14.0625 + -7.5x + x2 = 21 + 14.0625

Combine like terms: 21 + 14.0625 = 35.0625
14.0625 + -7.5x + x2 = 35.0625

Factor a perfect square on the left side:
(x + -3.75)(x + -3.75) = 35.0625

Calculate the square root of the right side: 5.921359641

Break this problem into two subproblems by setting 
(x + -3.75) equal to 5.921359641 and -5.921359641.

Subproblem 1

x + -3.75 = 5.921359641 Simplifying x + -3.75 = 5.921359641 Reorder the terms: -3.75 + x = 5.921359641 Solving -3.75 + x = 5.921359641 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.75' to each side of the equation. -3.75 + 3.75 + x = 5.921359641 + 3.75 Combine like terms: -3.75 + 3.75 = 0.00 0.00 + x = 5.921359641 + 3.75 x = 5.921359641 + 3.75 Combine like terms: 5.921359641 + 3.75 = 9.671359641 x = 9.671359641 Simplifying x = 9.671359641

Subproblem 2

x + -3.75 = -5.921359641 Simplifying x + -3.75 = -5.921359641 Reorder the terms: -3.75 + x = -5.921359641 Solving -3.75 + x = -5.921359641 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.75' to each side of the equation. -3.75 + 3.75 + x = -5.921359641 + 3.75 Combine like terms: -3.75 + 3.75 = 0.00 0.00 + x = -5.921359641 + 3.75 x = -5.921359641 + 3.75 Combine like terms: -5.921359641 + 3.75 = -2.171359641 x = -2.171359641 Simplifying x = -2.171359641

Solution

The solution to the problem is based on the solutions from the subproblems. x = {9.671359641, -2.171359641}

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