-4x^2+16x+81=

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Solution for -4x^2+16x+81= equation:


Simplifying
-4x2 + 16x + 81 = 0

Reorder the terms:
81 + 16x + -4x2 = 0

Solving
81 + 16x + -4x2 = 0

Solving for variable 'x'.

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

Divide each side by '-4'.
-20.25 + -4x + x2 = 0

Move the constant term to the right:

Add '20.25' to each side of the equation.
-20.25 + -4x + 20.25 + x2 = 0 + 20.25

Reorder the terms:
-20.25 + 20.25 + -4x + x2 = 0 + 20.25

Combine like terms: -20.25 + 20.25 = 0.00
0.00 + -4x + x2 = 0 + 20.25
-4x + x2 = 0 + 20.25

Combine like terms: 0 + 20.25 = 20.25
-4x + x2 = 20.25

The x term is -4x.  Take half its coefficient (-2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
-4x + 4 + x2 = 20.25 + 4

Reorder the terms:
4 + -4x + x2 = 20.25 + 4

Combine like terms: 20.25 + 4 = 24.25
4 + -4x + x2 = 24.25

Factor a perfect square on the left side:
(x + -2)(x + -2) = 24.25

Calculate the square root of the right side: 4.924428901

Break this problem into two subproblems by setting 
(x + -2) equal to 4.924428901 and -4.924428901.

Subproblem 1

x + -2 = 4.924428901 Simplifying x + -2 = 4.924428901 Reorder the terms: -2 + x = 4.924428901 Solving -2 + x = 4.924428901 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + x = 4.924428901 + 2 Combine like terms: -2 + 2 = 0 0 + x = 4.924428901 + 2 x = 4.924428901 + 2 Combine like terms: 4.924428901 + 2 = 6.924428901 x = 6.924428901 Simplifying x = 6.924428901

Subproblem 2

x + -2 = -4.924428901 Simplifying x + -2 = -4.924428901 Reorder the terms: -2 + x = -4.924428901 Solving -2 + x = -4.924428901 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + x = -4.924428901 + 2 Combine like terms: -2 + 2 = 0 0 + x = -4.924428901 + 2 x = -4.924428901 + 2 Combine like terms: -4.924428901 + 2 = -2.924428901 x = -2.924428901 Simplifying x = -2.924428901

Solution

The solution to the problem is based on the solutions from the subproblems. x = {6.924428901, -2.924428901}

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