-1x2 -7x +8 = 0
ax2 bx c = 0
a = -1
b = -7
c = 8
Δ = b2-4ac
Δ = -7² - (4 * -1 * 8)
Δ = 49 - (4*-8)
Δ = 49 - (-32)
Δ = 81 Δ > 0
-x2-7x+8=0
x = -b ∓ √Δ 2a
x' = 7 - √81 2*-1 = 7 - 9.0 -2 = -2.0 -2 = 1.0
x" = 7 + √81 2*-1 = 7 + 9.0 -2 = 16.0 -2 = -8.0
x' = 1.0
x" = -8.0
S = {x ∈ R / x' = 1.0, x" = -8.0 }