21=-x^2+56x+70

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Solution for 21=-x^2+56x+70 equation:


Simplifying
21 = -1x2 + 56x + 70

Reorder the terms:
21 = 70 + 56x + -1x2

Solving
21 = 70 + 56x + -1x2

Solving for variable 'x'.

Combine like terms: 21 + -70 = -49
-49 + -56x + x2 = 70 + 56x + -1x2 + -70 + -56x + x2

Reorder the terms:
-49 + -56x + x2 = 70 + -70 + 56x + -56x + -1x2 + x2

Combine like terms: 70 + -70 = 0
-49 + -56x + x2 = 0 + 56x + -56x + -1x2 + x2
-49 + -56x + x2 = 56x + -56x + -1x2 + x2

Combine like terms: 56x + -56x = 0
-49 + -56x + x2 = 0 + -1x2 + x2
-49 + -56x + x2 = -1x2 + x2

Combine like terms: -1x2 + x2 = 0
-49 + -56x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '49' to each side of the equation.
-49 + -56x + 49 + x2 = 0 + 49

Reorder the terms:
-49 + 49 + -56x + x2 = 0 + 49

Combine like terms: -49 + 49 = 0
0 + -56x + x2 = 0 + 49
-56x + x2 = 0 + 49

Combine like terms: 0 + 49 = 49
-56x + x2 = 49

The x term is -56x.  Take half its coefficient (-28).
Square it (784) and add it to both sides.

Add '784' to each side of the equation.
-56x + 784 + x2 = 49 + 784

Reorder the terms:
784 + -56x + x2 = 49 + 784

Combine like terms: 49 + 784 = 833
784 + -56x + x2 = 833

Factor a perfect square on the left side:
(x + -28)(x + -28) = 833

Calculate the square root of the right side: 28.861739379

Break this problem into two subproblems by setting 
(x + -28) equal to 28.861739379 and -28.861739379.

Subproblem 1

x + -28 = 28.861739379 Simplifying x + -28 = 28.861739379 Reorder the terms: -28 + x = 28.861739379 Solving -28 + x = 28.861739379 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '28' to each side of the equation. -28 + 28 + x = 28.861739379 + 28 Combine like terms: -28 + 28 = 0 0 + x = 28.861739379 + 28 x = 28.861739379 + 28 Combine like terms: 28.861739379 + 28 = 56.861739379 x = 56.861739379 Simplifying x = 56.861739379

Subproblem 2

x + -28 = -28.861739379 Simplifying x + -28 = -28.861739379 Reorder the terms: -28 + x = -28.861739379 Solving -28 + x = -28.861739379 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '28' to each side of the equation. -28 + 28 + x = -28.861739379 + 28 Combine like terms: -28 + 28 = 0 0 + x = -28.861739379 + 28 x = -28.861739379 + 28 Combine like terms: -28.861739379 + 28 = -0.861739379 x = -0.861739379 Simplifying x = -0.861739379

Solution

The solution to the problem is based on the solutions from the subproblems. x = {56.861739379, -0.861739379}

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