-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 = -18.0 -18 = 1.0
x" = -7 + √121 2*-9 = -7 + 11.0 -18 = 4.0 -18 = -0.222222222222
x' = 81.0
x" = -18.0
S = {x ∈ R / x' = 81.0, x" = -18.0 }