-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 }