r^2-4r+91=7

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Solution for r^2-4r+91=7 equation:


Simplifying
r2 + -4r + 91 = 7

Reorder the terms:
91 + -4r + r2 = 7

Solving
91 + -4r + r2 = 7

Solving for variable 'r'.

Reorder the terms:
91 + -7 + -4r + r2 = 7 + -7

Combine like terms: 91 + -7 = 84
84 + -4r + r2 = 7 + -7

Combine like terms: 7 + -7 = 0
84 + -4r + r2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-84' to each side of the equation.
84 + -4r + -84 + r2 = 0 + -84

Reorder the terms:
84 + -84 + -4r + r2 = 0 + -84

Combine like terms: 84 + -84 = 0
0 + -4r + r2 = 0 + -84
-4r + r2 = 0 + -84

Combine like terms: 0 + -84 = -84
-4r + r2 = -84

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 = -84 + 4

Reorder the terms:
4 + -4r + r2 = -84 + 4

Combine like terms: -84 + 4 = -80
4 + -4r + r2 = -80

Factor a perfect square on the left side:
(r + -2)(r + -2) = -80

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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