-4x2 -7x +15 = 0
ax2 bx c = 0
a = -4
b = -7
c = 15
Δ = b2-4ac
Δ = -7² - (4 * -4 * 15)
Δ = 49 - (4*-60)
Δ = 49 - (-240)
Δ = 289 Δ > 0
-4x2-7x+15=0
x = -b ∓ √Δ 2a
x' = 7 - √289 2*-4 = 7 - 17.0 -8 = -10.0 -8 = 1.25
x" = 7 + √289 2*-4 = 7 + 17.0 -8 = 24.0 -8 = -3.0
x' = 20.0
x" = -48.0
S = {x ∈ R / x' = 20.0, x" = -48.0 }