Question

y = - x² + 2x + 15 determine a raiz

Answer 1

∆=b² -4ac = 2² -4.(-1).15= 4+60= 64 => √∆=8
x = -b±√∆/2a
x = -2±8/2.(-1)
x' = -2+8/-2 = 6/-2 = -3 ✓
x" = -2-8/-2 = -10/-2 = 5 ✓

Answer 2

Y = - x² + 2x + 15

- x² + 2x + 15 = 0

a = - 1; b = 2; c = 15

∆ = b^2-4ac

∆ = 2^2 - 4.(-1).15

∆ = 4 + 60

∆ = 64

x = [- b +/- √∆]/2a

x = [ - 2 +/- √64]/2.(-1)

x = [ - 2 +/- 8]/(-2)

x' = [ - 2 - 8]/(-2) = -10/(-2) = 5

x" = [ - 2 + 8]/(-2) = 6/(-2) = - 3