18x2 +3x -15 = 0
ax2 bx c = 0
a = 18
b = 3
c = -15
Δ = b2-4ac
Δ = 3² - (4 * 18 * -15)
Δ = 9 - (4*-270)
Δ = 9 - (-1080)
Δ = 1089 Δ > 0
18x2+3x-15=0
x = -b ∓ √Δ 2a
x' = -3 - √1089 2*18 = -3 - 33.0 36 = -36.0 36 = -1.0
x" = -3 + √1089 2*18 = -3 + 33.0 36 = 30.0 36 = 0.833333333333
x' = -324.0
x" = 270.0
S = {x ∈ R / x' = -324.0, x" = 270.0 }