9r^2-8r-20=

Solution for 9r^2-8r-20= equation:

Simplifying
9r2 + -8r + -20 = 0

Reorder the terms:
-20 + -8r + 9r2 = 0

Solving
-20 + -8r + 9r2 = 0

Solving for variable 'r'.

Factor a trinomial.
(-10 + -9r)(2 + -1r) = 0

Subproblem 1
Set the factor '(-10 + -9r)' equal to zero and attempt to solve:

Simplifying
-10 + -9r = 0

Solving
-10 + -9r = 0

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

Add '10' to each side of the equation.
-10 + 10 + -9r = 0 + 10

Combine like terms: -10 + 10 = 0
0 + -9r = 0 + 10
-9r = 0 + 10

Combine like terms: 0 + 10 = 10
-9r = 10

Divide each side by '-9'.
r = -1.111111111

Simplifying
r = -1.111111111
Subproblem 2
Set the factor '(2 + -1r)' equal to zero and attempt to solve:

Simplifying
2 + -1r = 0

Solving
2 + -1r = 0

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

Add '-2' to each side of the equation.
2 + -2 + -1r = 0 + -2

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

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

Divide each side by '-1'.
r = 2

Simplifying
r = 2
Solution
r = {-1.111111111, 2}