-9x2 -7x +2 = 0
ax2 bx c = 0
a = -9
b = -7
c = 2
Δ = b2-4ac
Δ = -7² - (4 * -9 * 2)
Δ = 49 - (4*-18)
Δ = 49 - (-72)
Δ = 121 Δ > 0
-9x2-7x+2=0
x = -b ∓ √Δ 2a
x' = 7 - √121 2*-9 = 7 - 11.0 -18 = -4.0 -18 = 0.222222222222
x" = 7 + √121 2*-9 = 7 + 11.0 -18 = 18.0 -18 = -1.0
x' = 18.0
x" = -81.0
S = {x ∈ R / x' = 18.0, x" = -81.0 }