(x-3)(2x+1)=7

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Solution for (x-3)(2x+1)=7 equation:


Simplifying
(x + -3)(2x + 1) = 7

Reorder the terms:
(-3 + x)(2x + 1) = 7

Reorder the terms:
(-3 + x)(1 + 2x) = 7

Multiply (-3 + x) * (1 + 2x)
(-3(1 + 2x) + x(1 + 2x)) = 7
((1 * -3 + 2x * -3) + x(1 + 2x)) = 7
((-3 + -6x) + x(1 + 2x)) = 7
(-3 + -6x + (1 * x + 2x * x)) = 7
(-3 + -6x + (1x + 2x2)) = 7

Combine like terms: -6x + 1x = -5x
(-3 + -5x + 2x2) = 7

Solving
-3 + -5x + 2x2 = 7

Solving for variable 'x'.

Reorder the terms:
-3 + -7 + -5x + 2x2 = 7 + -7

Combine like terms: -3 + -7 = -10
-10 + -5x + 2x2 = 7 + -7

Combine like terms: 7 + -7 = 0
-10 + -5x + 2x2 = 0

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

Divide each side by '2'.
-5 + -2.5x + x2 = 0

Move the constant term to the right:

Add '5' to each side of the equation.
-5 + -2.5x + 5 + x2 = 0 + 5

Reorder the terms:
-5 + 5 + -2.5x + x2 = 0 + 5

Combine like terms: -5 + 5 = 0
0 + -2.5x + x2 = 0 + 5
-2.5x + x2 = 0 + 5

Combine like terms: 0 + 5 = 5
-2.5x + x2 = 5

The x term is -2.5x.  Take half its coefficient (-1.25).
Square it (1.5625) and add it to both sides.

Add '1.5625' to each side of the equation.
-2.5x + 1.5625 + x2 = 5 + 1.5625

Reorder the terms:
1.5625 + -2.5x + x2 = 5 + 1.5625

Combine like terms: 5 + 1.5625 = 6.5625
1.5625 + -2.5x + x2 = 6.5625

Factor a perfect square on the left side:
(x + -1.25)(x + -1.25) = 6.5625

Calculate the square root of the right side: 2.561737691

Break this problem into two subproblems by setting 
(x + -1.25) equal to 2.561737691 and -2.561737691.

Subproblem 1

x + -1.25 = 2.561737691 Simplifying x + -1.25 = 2.561737691 Reorder the terms: -1.25 + x = 2.561737691 Solving -1.25 + x = 2.561737691 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.25' to each side of the equation. -1.25 + 1.25 + x = 2.561737691 + 1.25 Combine like terms: -1.25 + 1.25 = 0.00 0.00 + x = 2.561737691 + 1.25 x = 2.561737691 + 1.25 Combine like terms: 2.561737691 + 1.25 = 3.811737691 x = 3.811737691 Simplifying x = 3.811737691

Subproblem 2

x + -1.25 = -2.561737691 Simplifying x + -1.25 = -2.561737691 Reorder the terms: -1.25 + x = -2.561737691 Solving -1.25 + x = -2.561737691 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.25' to each side of the equation. -1.25 + 1.25 + x = -2.561737691 + 1.25 Combine like terms: -1.25 + 1.25 = 0.00 0.00 + x = -2.561737691 + 1.25 x = -2.561737691 + 1.25 Combine like terms: -2.561737691 + 1.25 = -1.311737691 x = -1.311737691 Simplifying x = -1.311737691

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.811737691, -1.311737691}

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