Question

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

Answer 1

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)

Answer 2

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