4x^2+5x-21=-3

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Solution for 4x^2+5x-21=-3 equation:


Simplifying
4x2 + 5x + -21 = -3

Reorder the terms:
-21 + 5x + 4x2 = -3

Solving
-21 + 5x + 4x2 = -3

Solving for variable 'x'.

Reorder the terms:
-21 + 3 + 5x + 4x2 = -3 + 3

Combine like terms: -21 + 3 = -18
-18 + 5x + 4x2 = -3 + 3

Combine like terms: -3 + 3 = 0
-18 + 5x + 4x2 = 0

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

Divide each side by '4'.
-4.5 + 1.25x + x2 = 0

Move the constant term to the right:

Add '4.5' to each side of the equation.
-4.5 + 1.25x + 4.5 + x2 = 0 + 4.5

Reorder the terms:
-4.5 + 4.5 + 1.25x + x2 = 0 + 4.5

Combine like terms: -4.5 + 4.5 = 0.0
0.0 + 1.25x + x2 = 0 + 4.5
1.25x + x2 = 0 + 4.5

Combine like terms: 0 + 4.5 = 4.5
1.25x + x2 = 4.5

The x term is 1.25x.  Take half its coefficient (0.625).
Square it (0.390625) and add it to both sides.

Add '0.390625' to each side of the equation.
1.25x + 0.390625 + x2 = 4.5 + 0.390625

Reorder the terms:
0.390625 + 1.25x + x2 = 4.5 + 0.390625

Combine like terms: 4.5 + 0.390625 = 4.890625
0.390625 + 1.25x + x2 = 4.890625

Factor a perfect square on the left side:
(x + 0.625)(x + 0.625) = 4.890625

Calculate the square root of the right side: 2.211475752

Break this problem into two subproblems by setting 
(x + 0.625) equal to 2.211475752 and -2.211475752.

Subproblem 1

x + 0.625 = 2.211475752 Simplifying x + 0.625 = 2.211475752 Reorder the terms: 0.625 + x = 2.211475752 Solving 0.625 + x = 2.211475752 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.625' to each side of the equation. 0.625 + -0.625 + x = 2.211475752 + -0.625 Combine like terms: 0.625 + -0.625 = 0.000 0.000 + x = 2.211475752 + -0.625 x = 2.211475752 + -0.625 Combine like terms: 2.211475752 + -0.625 = 1.586475752 x = 1.586475752 Simplifying x = 1.586475752

Subproblem 2

x + 0.625 = -2.211475752 Simplifying x + 0.625 = -2.211475752 Reorder the terms: 0.625 + x = -2.211475752 Solving 0.625 + x = -2.211475752 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.625' to each side of the equation. 0.625 + -0.625 + x = -2.211475752 + -0.625 Combine like terms: 0.625 + -0.625 = 0.000 0.000 + x = -2.211475752 + -0.625 x = -2.211475752 + -0.625 Combine like terms: -2.211475752 + -0.625 = -2.836475752 x = -2.836475752 Simplifying x = -2.836475752

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.586475752, -2.836475752}

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