-4v^2+20v-21=0

Solution for -4v^2+20v-21=0 equation:

Simplifying
-4v2 + 20v + -21 = 0

Reorder the terms:
-21 + 20v + -4v2 = 0

Solving
-21 + 20v + -4v2 = 0

Solving for variable 'v'.

Factor a trinomial.
(-7 + 2v)(3 + -2v) = 0

Subproblem 1
Set the factor '(-7 + 2v)' equal to zero and attempt to solve:

Simplifying
-7 + 2v = 0

Solving
-7 + 2v = 0

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

Add '7' to each side of the equation.
-7 + 7 + 2v = 0 + 7

Combine like terms: -7 + 7 = 0
0 + 2v = 0 + 7
2v = 0 + 7

Combine like terms: 0 + 7 = 7
2v = 7

Divide each side by '2'.
v = 3.5

Simplifying
v = 3.5
Subproblem 2
Set the factor '(3 + -2v)' equal to zero and attempt to solve:

Simplifying
3 + -2v = 0

Solving
3 + -2v = 0

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

Add '-3' to each side of the equation.
3 + -3 + -2v = 0 + -3

Combine like terms: 3 + -3 = 0
0 + -2v = 0 + -3
-2v = 0 + -3

Combine like terms: 0 + -3 = -3
-2v = -3

Divide each side by '-2'.
v = 1.5

Simplifying
v = 1.5
Solution
v = {3.5, 1.5}