-1x2 +14x +15 = 0
ax2 bx c = 0
a = -1
b = 14
c = 15
Δ = b2-4ac
Δ = 14² - (4 * -1 * 15)
Δ = 196 - (4*-15)
Δ = 196 - (-60)
Δ = 256 Δ > 0
-x2+14x+15=0
x = -b ∓ √Δ 2a
x' = -14 - √256 2*-1 = -14 - 16.0 -2 = -30.0 -2 = 15.0
x" = -14 + √256 2*-1 = -14 + 16.0 -2 = 2.0 -2 = -1.0
x' = 15.0
x" = -1.0
S = {x ∈ R / x' = 15.0, x" = -1.0 }