81+(r^2)-(r^2)-2r-1=0

Solution for 81+(r^2)-(r^2)-2r-1=0 equation:

Simplifying
81 + (r2) + -1(r2) + -2r + -1 = 0
81 + r2 + -1(r2) + -2r + -1 = 0

Reorder the terms:
81 + -1 + -2r + r2 + -1r2 = 0

Combine like terms: 81 + -1 = 80
80 + -2r + r2 + -1r2 = 0

Combine like terms: r2 + -1r2 = 0
80 + -2r + 0 = 0
80 + -2r = 0

Solving
80 + -2r = 0

Solving for variable 'r'.

Move all terms containing r to the left, all other terms to the right.

Add '-80' to each side of the equation.
80 + -80 + -2r = 0 + -80

Combine like terms: 80 + -80 = 0
0 + -2r = 0 + -80
-2r = 0 + -80

Combine like terms: 0 + -80 = -80
-2r = -80

Divide each side by '-2'.
r = 40

Simplifying
r = 40