r^2-81=(r-9)(r-9)

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Solution for r^2-81=(r-9)(r-9) equation:


Simplifying
r2 + -81 = (r + -9)(r + -9)

Reorder the terms:
-81 + r2 = (r + -9)(r + -9)

Reorder the terms:
-81 + r2 = (-9 + r)(r + -9)

Reorder the terms:
-81 + r2 = (-9 + r)(-9 + r)

Multiply (-9 + r) * (-9 + r)
-81 + r2 = (-9(-9 + r) + r(-9 + r))
-81 + r2 = ((-9 * -9 + r * -9) + r(-9 + r))
-81 + r2 = ((81 + -9r) + r(-9 + r))
-81 + r2 = (81 + -9r + (-9 * r + r * r))
-81 + r2 = (81 + -9r + (-9r + r2))

Combine like terms: -9r + -9r = -18r
-81 + r2 = (81 + -18r + r2)

Add '-1r2' to each side of the equation.
-81 + r2 + -1r2 = 81 + -18r + r2 + -1r2

Combine like terms: r2 + -1r2 = 0
-81 + 0 = 81 + -18r + r2 + -1r2
-81 = 81 + -18r + r2 + -1r2

Combine like terms: r2 + -1r2 = 0
-81 = 81 + -18r + 0
-81 = 81 + -18r

Solving
-81 = 81 + -18r

Solving for variable 'r'.

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

Add '18r' to each side of the equation.
-81 + 18r = 81 + -18r + 18r

Combine like terms: -18r + 18r = 0
-81 + 18r = 81 + 0
-81 + 18r = 81

Add '81' to each side of the equation.
-81 + 81 + 18r = 81 + 81

Combine like terms: -81 + 81 = 0
0 + 18r = 81 + 81
18r = 81 + 81

Combine like terms: 81 + 81 = 162
18r = 162

Divide each side by '18'.
r = 9

Simplifying
r = 9

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