10r^2-21r+8=0

Solution for 10r^2-21r+8=0 equation:

Simplifying
10r2 + -21r + 8 = 0

Reorder the terms:
8 + -21r + 10r2 = 0

Solving
8 + -21r + 10r2 = 0

Solving for variable 'r'.

Factor a trinomial.
(1 + -2r)(8 + -5r) = 0

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

Simplifying
1 + -2r = 0

Solving
1 + -2r = 0

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

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

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

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

Divide each side by '-2'.
r = 0.5

Simplifying
r = 0.5
Subproblem 2
Set the factor '(8 + -5r)' equal to zero and attempt to solve:

Simplifying
8 + -5r = 0

Solving
8 + -5r = 0

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

Add '-8' to each side of the equation.
8 + -8 + -5r = 0 + -8

Combine like terms: 8 + -8 = 0
0 + -5r = 0 + -8
-5r = 0 + -8

Combine like terms: 0 + -8 = -8
-5r = -8

Divide each side by '-5'.
r = 1.6

Simplifying
r = 1.6
Solution
r = {0.5, 1.6}