5x(7-x)=18

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Solution for 5x(7-x)=18 equation:


Simplifying
5x(7 + -1x) = 18
(7 * 5x + -1x * 5x) = 18
(35x + -5x2) = 18

Solving
35x + -5x2 = 18

Solving for variable 'x'.

Reorder the terms:
-18 + 35x + -5x2 = 18 + -18

Combine like terms: 18 + -18 = 0
-18 + 35x + -5x2 = 0

Begin completing the square.  Divide all terms by
-5 the coefficient of the squared term: 

Divide each side by '-5'.
3.6 + -7x + x2 = 0

Move the constant term to the right:

Add '-3.6' to each side of the equation.
3.6 + -7x + -3.6 + x2 = 0 + -3.6

Reorder the terms:
3.6 + -3.6 + -7x + x2 = 0 + -3.6

Combine like terms: 3.6 + -3.6 = 0.0
0.0 + -7x + x2 = 0 + -3.6
-7x + x2 = 0 + -3.6

Combine like terms: 0 + -3.6 = -3.6
-7x + x2 = -3.6

The x term is -7x.  Take half its coefficient (-3.5).
Square it (12.25) and add it to both sides.

Add '12.25' to each side of the equation.
-7x + 12.25 + x2 = -3.6 + 12.25

Reorder the terms:
12.25 + -7x + x2 = -3.6 + 12.25

Combine like terms: -3.6 + 12.25 = 8.65
12.25 + -7x + x2 = 8.65

Factor a perfect square on the left side:
(x + -3.5)(x + -3.5) = 8.65

Calculate the square root of the right side: 2.941088234

Break this problem into two subproblems by setting 
(x + -3.5) equal to 2.941088234 and -2.941088234.

Subproblem 1

x + -3.5 = 2.941088234 Simplifying x + -3.5 = 2.941088234 Reorder the terms: -3.5 + x = 2.941088234 Solving -3.5 + x = 2.941088234 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.5' to each side of the equation. -3.5 + 3.5 + x = 2.941088234 + 3.5 Combine like terms: -3.5 + 3.5 = 0.0 0.0 + x = 2.941088234 + 3.5 x = 2.941088234 + 3.5 Combine like terms: 2.941088234 + 3.5 = 6.441088234 x = 6.441088234 Simplifying x = 6.441088234

Subproblem 2

x + -3.5 = -2.941088234 Simplifying x + -3.5 = -2.941088234 Reorder the terms: -3.5 + x = -2.941088234 Solving -3.5 + x = -2.941088234 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.5' to each side of the equation. -3.5 + 3.5 + x = -2.941088234 + 3.5 Combine like terms: -3.5 + 3.5 = 0.0 0.0 + x = -2.941088234 + 3.5 x = -2.941088234 + 3.5 Combine like terms: -2.941088234 + 3.5 = 0.558911766 x = 0.558911766 Simplifying x = 0.558911766

Solution

The solution to the problem is based on the solutions from the subproblems. x = {6.441088234, 0.558911766}

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