word problem: The demand and supply equations for a certain

The demand and supply equations for a certain item are given by:

D = –5p + 40
S = –p2 + 30p – 8

Find the equilibrium price.

At equilibrium, we have D = S. Then:

-5p + 40 = -p^2 + 30p - 8

p^2 - 35p + 48 = 0

p = [35+/-rt{(-35)^2-192}]/2p = 35 + 13.85/2

Still does not match. please help me?
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Edited by stapel -- Reason for edit: formatting

p^2-35p+48=0 quadratic equation

ax^2+bx+c=0
x=-b +/-[b^2-4ac]^1/2 all over 2a

p=35 +/-[35^2-192]^1/2 all over 2
p=35+/- [1225-192]^1/2 all over 2
p=35 +/- 32.14 all over 2
p=67.14/2 or p= 2.86/2
p=33.57 or p=1.43

Arthur