Question

2n^2 - 20
n= 5
?????

Answer 1

2n^2-20=0
2n^2=20
n^2=20÷2
n^2=10
n=radical 10

Answer 2

Use this:

n1,2 = -b +- √b²-4*a*c / 2a

a = 2n (2)
b = -20
c = -5 (you have to subtract 5 to get 0)