7r^2-21r=28

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Solution for 7r^2-21r=28 equation:


Simplifying
7r2 + -21r = 28

Reorder the terms:
-21r + 7r2 = 28

Solving
-21r + 7r2 = 28

Solving for variable 'r'.

Reorder the terms:
-28 + -21r + 7r2 = 28 + -28

Combine like terms: 28 + -28 = 0
-28 + -21r + 7r2 = 0

Factor out the Greatest Common Factor (GCF), '7'.
7(-4 + -3r + r2) = 0

Factor a trinomial.
7((-1 + -1r)(4 + -1r)) = 0

Ignore the factor 7.

Subproblem 1

Set the factor '(-1 + -1r)' equal to zero and attempt to solve: Simplifying -1 + -1r = 0 Solving -1 + -1r = 0 Move all terms containing r to the left, all other terms to the right. Add '1' to each side of the equation. -1 + 1 + -1r = 0 + 1 Combine like terms: -1 + 1 = 0 0 + -1r = 0 + 1 -1r = 0 + 1 Combine like terms: 0 + 1 = 1 -1r = 1 Divide each side by '-1'. r = -1 Simplifying r = -1

Subproblem 2

Set the factor '(4 + -1r)' equal to zero and attempt to solve: Simplifying 4 + -1r = 0 Solving 4 + -1r = 0 Move all terms containing r to the left, all other terms to the right. Add '-4' to each side of the equation. 4 + -4 + -1r = 0 + -4 Combine like terms: 4 + -4 = 0 0 + -1r = 0 + -4 -1r = 0 + -4 Combine like terms: 0 + -4 = -4 -1r = -4 Divide each side by '-1'. r = 4 Simplifying r = 4

Solution

r = {-1, 4}

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