4x^2+7x=400

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Solution for 4x^2+7x=400 equation:


Simplifying
4x2 + 7x = 400

Reorder the terms:
7x + 4x2 = 400

Solving
7x + 4x2 = 400

Solving for variable 'x'.

Reorder the terms:
-400 + 7x + 4x2 = 400 + -400

Combine like terms: 400 + -400 = 0
-400 + 7x + 4x2 = 0

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

Divide each side by '4'.
-100 + 1.75x + x2 = 0

Move the constant term to the right:

Add '100' to each side of the equation.
-100 + 1.75x + 100 + x2 = 0 + 100

Reorder the terms:
-100 + 100 + 1.75x + x2 = 0 + 100

Combine like terms: -100 + 100 = 0
0 + 1.75x + x2 = 0 + 100
1.75x + x2 = 0 + 100

Combine like terms: 0 + 100 = 100
1.75x + x2 = 100

The x term is 1.75x.  Take half its coefficient (0.875).
Square it (0.765625) and add it to both sides.

Add '0.765625' to each side of the equation.
1.75x + 0.765625 + x2 = 100 + 0.765625

Reorder the terms:
0.765625 + 1.75x + x2 = 100 + 0.765625

Combine like terms: 100 + 0.765625 = 100.765625
0.765625 + 1.75x + x2 = 100.765625

Factor a perfect square on the left side:
(x + 0.875)(x + 0.875) = 100.765625

Calculate the square root of the right side: 10.038208256

Break this problem into two subproblems by setting 
(x + 0.875) equal to 10.038208256 and -10.038208256.

Subproblem 1

x + 0.875 = 10.038208256 Simplifying x + 0.875 = 10.038208256 Reorder the terms: 0.875 + x = 10.038208256 Solving 0.875 + x = 10.038208256 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.875' to each side of the equation. 0.875 + -0.875 + x = 10.038208256 + -0.875 Combine like terms: 0.875 + -0.875 = 0.000 0.000 + x = 10.038208256 + -0.875 x = 10.038208256 + -0.875 Combine like terms: 10.038208256 + -0.875 = 9.163208256 x = 9.163208256 Simplifying x = 9.163208256

Subproblem 2

x + 0.875 = -10.038208256 Simplifying x + 0.875 = -10.038208256 Reorder the terms: 0.875 + x = -10.038208256 Solving 0.875 + x = -10.038208256 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.875' to each side of the equation. 0.875 + -0.875 + x = -10.038208256 + -0.875 Combine like terms: 0.875 + -0.875 = 0.000 0.000 + x = -10.038208256 + -0.875 x = -10.038208256 + -0.875 Combine like terms: -10.038208256 + -0.875 = -10.913208256 x = -10.913208256 Simplifying x = -10.913208256

Solution

The solution to the problem is based on the solutions from the subproblems. x = {9.163208256, -10.913208256}

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