18x2 -17x -15 = 0
ax2 bx c = 0
a = 18
b = -17
c = -15
Δ = b2-4ac
Δ = -17² - (4 * 18 * -15)
Δ = 289 - (4*-270)
Δ = 289 - (-1080)
Δ = 1369 Δ > 0
18x2-17x-15=0
x = -b ∓ √Δ 2a
x' = 17 - √1369 2*18 = 17 - 37.0 36 = -20.0 36 = -0.555555555556
x" = 17 + √1369 2*18 = 17 + 37.0 36 = 54.0 36 = 1.5
x' = -180.0
x" = 486.0
S = {x ∈ R / x' = -180.0, x" = 486.0 }