-z^2-7z+20=0

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Solution for -z^2-7z+20=0 equation:


Simplifying
-1z2 + -7z + 20 = 0

Reorder the terms:
20 + -7z + -1z2 = 0

Solving
20 + -7z + -1z2 = 0

Solving for variable 'z'.

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
-20 + 7z + z2 = 0

Move the constant term to the right:

Add '20' to each side of the equation.
-20 + 7z + 20 + z2 = 0 + 20

Reorder the terms:
-20 + 20 + 7z + z2 = 0 + 20

Combine like terms: -20 + 20 = 0
0 + 7z + z2 = 0 + 20
7z + z2 = 0 + 20

Combine like terms: 0 + 20 = 20
7z + z2 = 20

The z term is 7z.  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.
7z + 12.25 + z2 = 20 + 12.25

Reorder the terms:
12.25 + 7z + z2 = 20 + 12.25

Combine like terms: 20 + 12.25 = 32.25
12.25 + 7z + z2 = 32.25

Factor a perfect square on the left side:
(z + 3.5)(z + 3.5) = 32.25

Calculate the square root of the right side: 5.678908346

Break this problem into two subproblems by setting 
(z + 3.5) equal to 5.678908346 and -5.678908346.

Subproblem 1

z + 3.5 = 5.678908346 Simplifying z + 3.5 = 5.678908346 Reorder the terms: 3.5 + z = 5.678908346 Solving 3.5 + z = 5.678908346 Solving for variable 'z'. Move all terms containing z to the left, all other terms to the right. Add '-3.5' to each side of the equation. 3.5 + -3.5 + z = 5.678908346 + -3.5 Combine like terms: 3.5 + -3.5 = 0.0 0.0 + z = 5.678908346 + -3.5 z = 5.678908346 + -3.5 Combine like terms: 5.678908346 + -3.5 = 2.178908346 z = 2.178908346 Simplifying z = 2.178908346

Subproblem 2

z + 3.5 = -5.678908346 Simplifying z + 3.5 = -5.678908346 Reorder the terms: 3.5 + z = -5.678908346 Solving 3.5 + z = -5.678908346 Solving for variable 'z'. Move all terms containing z to the left, all other terms to the right. Add '-3.5' to each side of the equation. 3.5 + -3.5 + z = -5.678908346 + -3.5 Combine like terms: 3.5 + -3.5 = 0.0 0.0 + z = -5.678908346 + -3.5 z = -5.678908346 + -3.5 Combine like terms: -5.678908346 + -3.5 = -9.178908346 z = -9.178908346 Simplifying z = -9.178908346

Solution

The solution to the problem is based on the solutions from the subproblems. z = {2.178908346, -9.178908346}

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