r^2+15=4r

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Solution for r^2+15=4r equation:


Simplifying
r2 + 15 = 4r

Reorder the terms:
15 + r2 = 4r

Solving
15 + r2 = 4r

Solving for variable 'r'.

Reorder the terms:
15 + -4r + r2 = 4r + -4r

Combine like terms: 4r + -4r = 0
15 + -4r + r2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-15' to each side of the equation.
15 + -4r + -15 + r2 = 0 + -15

Reorder the terms:
15 + -15 + -4r + r2 = 0 + -15

Combine like terms: 15 + -15 = 0
0 + -4r + r2 = 0 + -15
-4r + r2 = 0 + -15

Combine like terms: 0 + -15 = -15
-4r + r2 = -15

The r term is -4r.  Take half its coefficient (-2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
-4r + 4 + r2 = -15 + 4

Reorder the terms:
4 + -4r + r2 = -15 + 4

Combine like terms: -15 + 4 = -11
4 + -4r + r2 = -11

Factor a perfect square on the left side:
(r + -2)(r + -2) = -11

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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