18x2 +15x -3 = 0
ax2 bx c = 0
a = 18
b = 15
c = -3
Δ = b2-4ac
Δ = 15² - (4 * 18 * -3)
Δ = 225 - (4*-54)
Δ = 225 - (-216)
Δ = 441 Δ > 0
18x2+15x-3=0
x = -b ∓ √Δ 2a
x' = -15 - √441 2*18 = -15 - 21.0 36 = -36.0 36 = -1.0
x" = -15 + √441 2*18 = -15 + 21.0 36 = 6.0 36 = 0.166666666667
x' = -324.0
x" = 54.0
S = {x ∈ R / x' = -324.0, x" = 54.0 }