-5x^2+40x-78=

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Solution for -5x^2+40x-78= equation:


Simplifying
-5x2 + 40x + -78 = 0

Reorder the terms:
-78 + 40x + -5x2 = 0

Solving
-78 + 40x + -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'.
15.6 + -8x + x2 = 0

Move the constant term to the right:

Add '-15.6' to each side of the equation.
15.6 + -8x + -15.6 + x2 = 0 + -15.6

Reorder the terms:
15.6 + -15.6 + -8x + x2 = 0 + -15.6

Combine like terms: 15.6 + -15.6 = 0.0
0.0 + -8x + x2 = 0 + -15.6
-8x + x2 = 0 + -15.6

Combine like terms: 0 + -15.6 = -15.6
-8x + x2 = -15.6

The x term is -8x.  Take half its coefficient (-4).
Square it (16) and add it to both sides.

Add '16' to each side of the equation.
-8x + 16 + x2 = -15.6 + 16

Reorder the terms:
16 + -8x + x2 = -15.6 + 16

Combine like terms: -15.6 + 16 = 0.4
16 + -8x + x2 = 0.4

Factor a perfect square on the left side:
(x + -4)(x + -4) = 0.4

Calculate the square root of the right side: 0.632455532

Break this problem into two subproblems by setting 
(x + -4) equal to 0.632455532 and -0.632455532.

Subproblem 1

x + -4 = 0.632455532 Simplifying x + -4 = 0.632455532 Reorder the terms: -4 + x = 0.632455532 Solving -4 + x = 0.632455532 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '4' to each side of the equation. -4 + 4 + x = 0.632455532 + 4 Combine like terms: -4 + 4 = 0 0 + x = 0.632455532 + 4 x = 0.632455532 + 4 Combine like terms: 0.632455532 + 4 = 4.632455532 x = 4.632455532 Simplifying x = 4.632455532

Subproblem 2

x + -4 = -0.632455532 Simplifying x + -4 = -0.632455532 Reorder the terms: -4 + x = -0.632455532 Solving -4 + x = -0.632455532 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '4' to each side of the equation. -4 + 4 + x = -0.632455532 + 4 Combine like terms: -4 + 4 = 0 0 + x = -0.632455532 + 4 x = -0.632455532 + 4 Combine like terms: -0.632455532 + 4 = 3.367544468 x = 3.367544468 Simplifying x = 3.367544468

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.632455532, 3.367544468}

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