(X-7)(X+5)=90

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Solution for (X-7)(X+5)=90 equation:


Simplifying
(X + -7)(X + 5) = 90

Reorder the terms:
(-7 + X)(X + 5) = 90

Reorder the terms:
(-7 + X)(5 + X) = 90

Multiply (-7 + X) * (5 + X)
(-7(5 + X) + X(5 + X)) = 90
((5 * -7 + X * -7) + X(5 + X)) = 90
((-35 + -7X) + X(5 + X)) = 90
(-35 + -7X + (5 * X + X * X)) = 90
(-35 + -7X + (5X + X2)) = 90

Combine like terms: -7X + 5X = -2X
(-35 + -2X + X2) = 90

Solving
-35 + -2X + X2 = 90

Solving for variable 'X'.

Reorder the terms:
-35 + -90 + -2X + X2 = 90 + -90

Combine like terms: -35 + -90 = -125
-125 + -2X + X2 = 90 + -90

Combine like terms: 90 + -90 = 0
-125 + -2X + X2 = 0

Begin completing the square.

Move the constant term to the right:

Add '125' to each side of the equation.
-125 + -2X + 125 + X2 = 0 + 125

Reorder the terms:
-125 + 125 + -2X + X2 = 0 + 125

Combine like terms: -125 + 125 = 0
0 + -2X + X2 = 0 + 125
-2X + X2 = 0 + 125

Combine like terms: 0 + 125 = 125
-2X + X2 = 125

The X term is -2X.  Take half its coefficient (-1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
-2X + 1 + X2 = 125 + 1

Reorder the terms:
1 + -2X + X2 = 125 + 1

Combine like terms: 125 + 1 = 126
1 + -2X + X2 = 126

Factor a perfect square on the left side:
(X + -1)(X + -1) = 126

Calculate the square root of the right side: 11.22497216

Break this problem into two subproblems by setting 
(X + -1) equal to 11.22497216 and -11.22497216.

Subproblem 1

X + -1 = 11.22497216 Simplifying X + -1 = 11.22497216 Reorder the terms: -1 + X = 11.22497216 Solving -1 + X = 11.22497216 Solving for variable 'X'. Move all terms containing X to the left, all other terms to the right. Add '1' to each side of the equation. -1 + 1 + X = 11.22497216 + 1 Combine like terms: -1 + 1 = 0 0 + X = 11.22497216 + 1 X = 11.22497216 + 1 Combine like terms: 11.22497216 + 1 = 12.22497216 X = 12.22497216 Simplifying X = 12.22497216

Subproblem 2

X + -1 = -11.22497216 Simplifying X + -1 = -11.22497216 Reorder the terms: -1 + X = -11.22497216 Solving -1 + X = -11.22497216 Solving for variable 'X'. Move all terms containing X to the left, all other terms to the right. Add '1' to each side of the equation. -1 + 1 + X = -11.22497216 + 1 Combine like terms: -1 + 1 = 0 0 + X = -11.22497216 + 1 X = -11.22497216 + 1 Combine like terms: -11.22497216 + 1 = -10.22497216 X = -10.22497216 Simplifying X = -10.22497216

Solution

The solution to the problem is based on the solutions from the subproblems. X = {12.22497216, -10.22497216}

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