X^2+7X=90

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Solution for X^2+7X=90 equation:


Simplifying
X2 + 7X = 90

Reorder the terms:
7X + X2 = 90

Solving
7X + X2 = 90

Solving for variable 'X'.

Reorder the terms:
-90 + 7X + X2 = 90 + -90

Combine like terms: 90 + -90 = 0
-90 + 7X + X2 = 0

Begin completing the square.

Move the constant term to the right:

Add '90' to each side of the equation.
-90 + 7X + 90 + X2 = 0 + 90

Reorder the terms:
-90 + 90 + 7X + X2 = 0 + 90

Combine like terms: -90 + 90 = 0
0 + 7X + X2 = 0 + 90
7X + X2 = 0 + 90

Combine like terms: 0 + 90 = 90
7X + X2 = 90

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 = 90 + 12.25

Reorder the terms:
12.25 + 7X + X2 = 90 + 12.25

Combine like terms: 90 + 12.25 = 102.25
12.25 + 7X + X2 = 102.25

Factor a perfect square on the left side:
(X + 3.5)(X + 3.5) = 102.25

Calculate the square root of the right side: 10.111874208

Break this problem into two subproblems by setting 
(X + 3.5) equal to 10.111874208 and -10.111874208.

Subproblem 1

X + 3.5 = 10.111874208 Simplifying X + 3.5 = 10.111874208 Reorder the terms: 3.5 + X = 10.111874208 Solving 3.5 + X = 10.111874208 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 = 10.111874208 + -3.5 Combine like terms: 3.5 + -3.5 = 0.0 0.0 + X = 10.111874208 + -3.5 X = 10.111874208 + -3.5 Combine like terms: 10.111874208 + -3.5 = 6.611874208 X = 6.611874208 Simplifying X = 6.611874208

Subproblem 2

X + 3.5 = -10.111874208 Simplifying X + 3.5 = -10.111874208 Reorder the terms: 3.5 + X = -10.111874208 Solving 3.5 + X = -10.111874208 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 = -10.111874208 + -3.5 Combine like terms: 3.5 + -3.5 = 0.0 0.0 + X = -10.111874208 + -3.5 X = -10.111874208 + -3.5 Combine like terms: -10.111874208 + -3.5 = -13.611874208 X = -13.611874208 Simplifying X = -13.611874208

Solution

The solution to the problem is based on the solutions from the subproblems. X = {6.611874208, -13.611874208}

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