r^4=r^3+28r^2

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Solution for r^4=r^3+28r^2 equation:


Simplifying
r4 = r3 + 28r2

Reorder the terms:
r4 = 28r2 + r3

Solving
r4 = 28r2 + r3

Solving for variable 'r'.

Reorder the terms:
-28r2 + -1r3 + r4 = 28r2 + r3 + -28r2 + -1r3

Reorder the terms:
-28r2 + -1r3 + r4 = 28r2 + -28r2 + r3 + -1r3

Combine like terms: 28r2 + -28r2 = 0
-28r2 + -1r3 + r4 = 0 + r3 + -1r3
-28r2 + -1r3 + r4 = r3 + -1r3

Combine like terms: r3 + -1r3 = 0
-28r2 + -1r3 + r4 = 0

Factor out the Greatest Common Factor (GCF), 'r2'.
r2(-28 + -1r + r2) = 0

Subproblem 1

Set the factor 'r2' equal to zero and attempt to solve: Simplifying r2 = 0 Solving r2 = 0 Move all terms containing r to the left, all other terms to the right. Simplifying r2 = 0 Take the square root of each side: r = {0}

Subproblem 2

Set the factor '(-28 + -1r + r2)' equal to zero and attempt to solve: Simplifying -28 + -1r + r2 = 0 Solving -28 + -1r + r2 = 0 Begin completing the square. Move the constant term to the right: Add '28' to each side of the equation. -28 + -1r + 28 + r2 = 0 + 28 Reorder the terms: -28 + 28 + -1r + r2 = 0 + 28 Combine like terms: -28 + 28 = 0 0 + -1r + r2 = 0 + 28 -1r + r2 = 0 + 28 Combine like terms: 0 + 28 = 28 -1r + r2 = 28 The r term is -1r. Take half its coefficient (-0.5). Square it (0.25) and add it to both sides. Add '0.25' to each side of the equation. -1r + 0.25 + r2 = 28 + 0.25 Reorder the terms: 0.25 + -1r + r2 = 28 + 0.25 Combine like terms: 28 + 0.25 = 28.25 0.25 + -1r + r2 = 28.25 Factor a perfect square on the left side: (r + -0.5)(r + -0.5) = 28.25 Calculate the square root of the right side: 5.315072906 Break this problem into two subproblems by setting (r + -0.5) equal to 5.315072906 and -5.315072906.

Subproblem 1

r + -0.5 = 5.315072906 Simplifying r + -0.5 = 5.315072906 Reorder the terms: -0.5 + r = 5.315072906 Solving -0.5 + r = 5.315072906 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '0.5' to each side of the equation. -0.5 + 0.5 + r = 5.315072906 + 0.5 Combine like terms: -0.5 + 0.5 = 0.0 0.0 + r = 5.315072906 + 0.5 r = 5.315072906 + 0.5 Combine like terms: 5.315072906 + 0.5 = 5.815072906 r = 5.815072906 Simplifying r = 5.815072906

Subproblem 2

r + -0.5 = -5.315072906 Simplifying r + -0.5 = -5.315072906 Reorder the terms: -0.5 + r = -5.315072906 Solving -0.5 + r = -5.315072906 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '0.5' to each side of the equation. -0.5 + 0.5 + r = -5.315072906 + 0.5 Combine like terms: -0.5 + 0.5 = 0.0 0.0 + r = -5.315072906 + 0.5 r = -5.315072906 + 0.5 Combine like terms: -5.315072906 + 0.5 = -4.815072906 r = -4.815072906 Simplifying r = -4.815072906

Solution

The solution to the problem is based on the solutions from the subproblems. r = {5.815072906, -4.815072906}

Solution

r = {0, 5.815072906, -4.815072906}

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