-1x2 +9x +10 = 0
ax2 bx c = 0
a = -1
b = 9
c = 10
Δ = b2-4ac
Δ = 9² - (4 * -1 * 10)
Δ = 81 - (4*-10)
Δ = 81 - (-40)
Δ = 121 Δ > 0
-x2+9x+10=0
x = -b ∓ √Δ 2a
x' = -9 - √121 2*-1 = -9 - 11.0 -2 = -20.0 -2 = 10.0
x" = -9 + √121 2*-1 = -9 + 11.0 -2 = 2.0 -2 = -1.0
x' = 10.0
x" = -1.0
S = {x ∈ R / x' = 10.0, x" = -1.0 }