-1x2 +8x -7 = 0
ax2 bx c = 0
a = -1
b = 8
c = -7
Δ = b2-4ac
Δ = 8² - (4 * -1 * -7)
Δ = 64 - (4*7)
Δ = 64 - (28)
Δ = 36 Δ > 0
-x2+8x-7=0
x = -b ∓ √Δ 2a
x' = -8 - √36 2*-1 = -8 - 6.0 -2 = -14.0 -2 = 7.0
x" = -8 + √36 2*-1 = -8 + 6.0 -2 = -2.0 -2 = 1.0
x' = 7.0
x" = 1.0
S = {x ∈ R / x' = 7.0, x" = 1.0 }