5x2 -14x +9 = 0
ax2 bx c = 0
a = 5
b = -14
c = 9
Δ = b2-4ac
Δ = -14² - (4 * 5 * 9)
Δ = 196 - (4*45)
Δ = 196 - (180)
Δ = 16 Δ > 0
5x2-14x+9=0
x = -b ∓ √Δ 2a
x' = 14 - √16 2*5 = 14 - 4.0 10 = 10.0 10 = 1.0
x" = 14 + √16 2*5 = 14 + 4.0 10 = 18.0 10 = 1.8
x' = 25.0
x" = 45.0
S = {x ∈ R / x' = 25.0, x" = 45.0 }