15x2 -4x -19 = 0
ax2 bx c = 0
a = 15
b = -4
c = -19
Δ = b2-4ac
Δ = -4² - (4 * 15 * -19)
Δ = 16 - (4*-285)
Δ = 16 - (-1140)
Δ = 1156 Δ > 0
15x2-4x-19=0
x = -b ∓ √Δ 2a
x' = 4 - √1156 2*15 = 4 - 34.0 30 = -30.0 30 = -1.0
x" = 4 + √1156 2*15 = 4 + 34.0 30 = 38.0 30 = 1.26666666667
x' = -225.0
x" = 285.0
S = {x ∈ R / x' = -225.0, x" = 285.0 }