4r^2+5r-5=0

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Solution for 4r^2+5r-5=0 equation:


Simplifying
4r2 + 5r + -5 = 0

Reorder the terms:
-5 + 5r + 4r2 = 0

Solving
-5 + 5r + 4r2 = 0

Solving for variable 'r'.

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

Divide each side by '4'.
-1.25 + 1.25r + r2 = 0

Move the constant term to the right:

Add '1.25' to each side of the equation.
-1.25 + 1.25r + 1.25 + r2 = 0 + 1.25

Reorder the terms:
-1.25 + 1.25 + 1.25r + r2 = 0 + 1.25

Combine like terms: -1.25 + 1.25 = 0.00
0.00 + 1.25r + r2 = 0 + 1.25
1.25r + r2 = 0 + 1.25

Combine like terms: 0 + 1.25 = 1.25
1.25r + r2 = 1.25

The r term is 1.25r.  Take half its coefficient (0.625).
Square it (0.390625) and add it to both sides.

Add '0.390625' to each side of the equation.
1.25r + 0.390625 + r2 = 1.25 + 0.390625

Reorder the terms:
0.390625 + 1.25r + r2 = 1.25 + 0.390625

Combine like terms: 1.25 + 0.390625 = 1.640625
0.390625 + 1.25r + r2 = 1.640625

Factor a perfect square on the left side:
(r + 0.625)(r + 0.625) = 1.640625

Calculate the square root of the right side: 1.280868846

Break this problem into two subproblems by setting 
(r + 0.625) equal to 1.280868846 and -1.280868846.

Subproblem 1

r + 0.625 = 1.280868846 Simplifying r + 0.625 = 1.280868846 Reorder the terms: 0.625 + r = 1.280868846 Solving 0.625 + r = 1.280868846 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-0.625' to each side of the equation. 0.625 + -0.625 + r = 1.280868846 + -0.625 Combine like terms: 0.625 + -0.625 = 0.000 0.000 + r = 1.280868846 + -0.625 r = 1.280868846 + -0.625 Combine like terms: 1.280868846 + -0.625 = 0.655868846 r = 0.655868846 Simplifying r = 0.655868846

Subproblem 2

r + 0.625 = -1.280868846 Simplifying r + 0.625 = -1.280868846 Reorder the terms: 0.625 + r = -1.280868846 Solving 0.625 + r = -1.280868846 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-0.625' to each side of the equation. 0.625 + -0.625 + r = -1.280868846 + -0.625 Combine like terms: 0.625 + -0.625 = 0.000 0.000 + r = -1.280868846 + -0.625 r = -1.280868846 + -0.625 Combine like terms: -1.280868846 + -0.625 = -1.905868846 r = -1.905868846 Simplifying r = -1.905868846

Solution

The solution to the problem is based on the solutions from the subproblems. r = {0.655868846, -1.905868846}

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