-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 = -54.0 -36 = 1.5
x" = -17 + √1369 2*-18 = -17 + 37.0 -36 = 20.0 -36 = -0.555555555556
x' = 486.0
x" = -180.0
S = {x ∈ R / x' = 486.0, x" = -180.0 }