20u^2+21u-5=0

Solution for 20u^2+21u-5=0 equation:

Simplifying
20u2 + 21u + -5 = 0

Reorder the terms:
-5 + 21u + 20u2 = 0

Solving
-5 + 21u + 20u2 = 0

Solving for variable 'u'.

Factor a trinomial.
(-5 + -4u)(1 + -5u) = 0

Subproblem 1
Set the factor '(-5 + -4u)' equal to zero and attempt to solve:

Simplifying
-5 + -4u = 0

Solving
-5 + -4u = 0

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

Add '5' to each side of the equation.
-5 + 5 + -4u = 0 + 5

Combine like terms: -5 + 5 = 0
0 + -4u = 0 + 5
-4u = 0 + 5

Combine like terms: 0 + 5 = 5
-4u = 5

Divide each side by '-4'.
u = -1.25

Simplifying
u = -1.25
Subproblem 2
Set the factor '(1 + -5u)' equal to zero and attempt to solve:

Simplifying
1 + -5u = 0

Solving
1 + -5u = 0

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

Add '-1' to each side of the equation.
1 + -1 + -5u = 0 + -1

Combine like terms: 1 + -1 = 0
0 + -5u = 0 + -1
-5u = 0 + -1

Combine like terms: 0 + -1 = -1
-5u = -1

Divide each side by '-5'.
u = 0.2

Simplifying
u = 0.2
Solution
u = {-1.25, 0.2}