-18x2 +19x +12 = 0
ax2 bx c = 0
a = -18
b = 19
c = 12
Δ = b2-4ac
Δ = 19² - (4 * -18 * 12)
Δ = 361 - (4*-216)
Δ = 361 - (-864)
Δ = 1225 Δ > 0
-18x2+19x+12=0
x = -b ∓ √Δ 2a
x' = -19 - √1225 2*-18 = -19 - 35.0 -36 = -54.0 -36 = 1.5
x" = -19 + √1225 2*-18 = -19 + 35.0 -36 = 16.0 -36 = -0.444444444444
x' = 486.0
x" = -144.0
S = {x ∈ R / x' = 486.0, x" = -144.0 }