Can comeone help me please and thanks?

Question

The demand and supply equations for a certain item are given by
D = -5p + 40
S = -p2 + 30p – 8
Find the equilibrium price.

A) $1.57 B) $1.29 C) $1.71 D) $1.43

Answer 1

Set these equations equal to each other: -5p+40=-p^2+30p-8 and then solve.
P^2-35P+48=0
Use the quadratic equation to solve this and you get 1.43$: D

Answer 2

-5p + 40 = -p^2 + 30p - 8
0 = p^2 - 35p + 48

(-b-sqrt(b^2-4*a*c)/2a = (35-sqrt(35^2-4*48))/2 = 1.43

The answer is D

Answer 3

$ 1 . 57 B