-9x2 +22x +15 = 0
ax2 bx c = 0
a = -9
b = 22
c = 15
Δ = b2-4ac
Δ = 22² - (4 * -9 * 15)
Δ = 484 - (4*-135)
Δ = 484 - (-540)
Δ = 1024 Δ > 0
-9x2+22x+15=0
x = -b ∓ √Δ 2a
x' = -22 - √1024 2*-9 = -22 - 32.0 -18 = -54.0 -18 = 3.0
x" = -22 + √1024 2*-9 = -22 + 32.0 -18 = 10.0 -18 = -0.555555555556
x' = 243.0
x" = -45.0
S = {x ∈ R / x' = 243.0, x" = -45.0 }