5r^2-8r+20=0

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Solution for 5r^2-8r+20=0 equation:


Simplifying
5r2 + -8r + 20 = 0

Reorder the terms:
20 + -8r + 5r2 = 0

Solving
20 + -8r + 5r2 = 0

Solving for variable 'r'.

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

Divide each side by '5'.
4 + -1.6r + r2 = 0

Move the constant term to the right:

Add '-4' to each side of the equation.
4 + -1.6r + -4 + r2 = 0 + -4

Reorder the terms:
4 + -4 + -1.6r + r2 = 0 + -4

Combine like terms: 4 + -4 = 0
0 + -1.6r + r2 = 0 + -4
-1.6r + r2 = 0 + -4

Combine like terms: 0 + -4 = -4
-1.6r + r2 = -4

The r term is -1.6r.  Take half its coefficient (-0.8).
Square it (0.64) and add it to both sides.

Add '0.64' to each side of the equation.
-1.6r + 0.64 + r2 = -4 + 0.64

Reorder the terms:
0.64 + -1.6r + r2 = -4 + 0.64

Combine like terms: -4 + 0.64 = -3.36
0.64 + -1.6r + r2 = -3.36

Factor a perfect square on the left side:
(r + -0.8)(r + -0.8) = -3.36

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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