-0.01*x^2+1.2*x-20=7

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Solution for -0.01*x^2+1.2*x-20=7 equation:


Simplifying
-0.01x2 + 1.2x + -20 = 7

Reorder the terms:
-20 + 1.2x + -0.01x2 = 7

Solving
-20 + 1.2x + -0.01x2 = 7

Solving for variable 'x'.

Reorder the terms:
-20 + -7 + 1.2x + -0.01x2 = 7 + -7

Combine like terms: -20 + -7 = -27
-27 + 1.2x + -0.01x2 = 7 + -7

Combine like terms: 7 + -7 = 0
-27 + 1.2x + -0.01x2 = 0

Begin completing the square.  Divide all terms by
-0.01 the coefficient of the squared term: 

Divide each side by '-0.01'.
2700 + -120x + x2 = 0

Move the constant term to the right:

Add '-2700' to each side of the equation.
2700 + -120x + -2700 + x2 = 0 + -2700

Reorder the terms:
2700 + -2700 + -120x + x2 = 0 + -2700

Combine like terms: 2700 + -2700 = 0
0 + -120x + x2 = 0 + -2700
-120x + x2 = 0 + -2700

Combine like terms: 0 + -2700 = -2700
-120x + x2 = -2700

The x term is -120x.  Take half its coefficient (-60).
Square it (3600) and add it to both sides.

Add '3600' to each side of the equation.
-120x + 3600 + x2 = -2700 + 3600

Reorder the terms:
3600 + -120x + x2 = -2700 + 3600

Combine like terms: -2700 + 3600 = 900
3600 + -120x + x2 = 900

Factor a perfect square on the left side:
(x + -60)(x + -60) = 900

Calculate the square root of the right side: 30

Break this problem into two subproblems by setting 
(x + -60) equal to 30 and -30.

Subproblem 1

x + -60 = 30 Simplifying x + -60 = 30 Reorder the terms: -60 + x = 30 Solving -60 + x = 30 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '60' to each side of the equation. -60 + 60 + x = 30 + 60 Combine like terms: -60 + 60 = 0 0 + x = 30 + 60 x = 30 + 60 Combine like terms: 30 + 60 = 90 x = 90 Simplifying x = 90

Subproblem 2

x + -60 = -30 Simplifying x + -60 = -30 Reorder the terms: -60 + x = -30 Solving -60 + x = -30 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '60' to each side of the equation. -60 + 60 + x = -30 + 60 Combine like terms: -60 + 60 = 0 0 + x = -30 + 60 x = -30 + 60 Combine like terms: -30 + 60 = 30 x = 30 Simplifying x = 30

Solution

The solution to the problem is based on the solutions from the subproblems. x = {90, 30}

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