(7-x)(3+4x)=9

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Solution for (7-x)(3+4x)=9 equation:


Simplifying
(7 + -1x)(3 + 4x) = 9

Multiply (7 + -1x) * (3 + 4x)
(7(3 + 4x) + -1x * (3 + 4x)) = 9
((3 * 7 + 4x * 7) + -1x * (3 + 4x)) = 9
((21 + 28x) + -1x * (3 + 4x)) = 9
(21 + 28x + (3 * -1x + 4x * -1x)) = 9
(21 + 28x + (-3x + -4x2)) = 9

Combine like terms: 28x + -3x = 25x
(21 + 25x + -4x2) = 9

Solving
21 + 25x + -4x2 = 9

Solving for variable 'x'.

Reorder the terms:
21 + -9 + 25x + -4x2 = 9 + -9

Combine like terms: 21 + -9 = 12
12 + 25x + -4x2 = 9 + -9

Combine like terms: 9 + -9 = 0
12 + 25x + -4x2 = 0

Begin completing the square.  Divide all terms by
-4 the coefficient of the squared term: 

Divide each side by '-4'.
-3 + -6.25x + x2 = 0

Move the constant term to the right:

Add '3' to each side of the equation.
-3 + -6.25x + 3 + x2 = 0 + 3

Reorder the terms:
-3 + 3 + -6.25x + x2 = 0 + 3

Combine like terms: -3 + 3 = 0
0 + -6.25x + x2 = 0 + 3
-6.25x + x2 = 0 + 3

Combine like terms: 0 + 3 = 3
-6.25x + x2 = 3

The x term is -6.25x.  Take half its coefficient (-3.125).
Square it (9.765625) and add it to both sides.

Add '9.765625' to each side of the equation.
-6.25x + 9.765625 + x2 = 3 + 9.765625

Reorder the terms:
9.765625 + -6.25x + x2 = 3 + 9.765625

Combine like terms: 3 + 9.765625 = 12.765625
9.765625 + -6.25x + x2 = 12.765625

Factor a perfect square on the left side:
(x + -3.125)(x + -3.125) = 12.765625

Calculate the square root of the right side: 3.572901482

Break this problem into two subproblems by setting 
(x + -3.125) equal to 3.572901482 and -3.572901482.

Subproblem 1

x + -3.125 = 3.572901482 Simplifying x + -3.125 = 3.572901482 Reorder the terms: -3.125 + x = 3.572901482 Solving -3.125 + x = 3.572901482 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.125' to each side of the equation. -3.125 + 3.125 + x = 3.572901482 + 3.125 Combine like terms: -3.125 + 3.125 = 0.000 0.000 + x = 3.572901482 + 3.125 x = 3.572901482 + 3.125 Combine like terms: 3.572901482 + 3.125 = 6.697901482 x = 6.697901482 Simplifying x = 6.697901482

Subproblem 2

x + -3.125 = -3.572901482 Simplifying x + -3.125 = -3.572901482 Reorder the terms: -3.125 + x = -3.572901482 Solving -3.125 + x = -3.572901482 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.125' to each side of the equation. -3.125 + 3.125 + x = -3.572901482 + 3.125 Combine like terms: -3.125 + 3.125 = 0.000 0.000 + x = -3.572901482 + 3.125 x = -3.572901482 + 3.125 Combine like terms: -3.572901482 + 3.125 = -0.447901482 x = -0.447901482 Simplifying x = -0.447901482

Solution

The solution to the problem is based on the solutions from the subproblems. x = {6.697901482, -0.447901482}

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