Question

resolva x²-3x-4=0 b) x²+8x+16=0 c) 3²-2x-1=0

Answer 1

a) x² - 3x - 4 = 0
Δ = b² - 4 · a · c
Δ = (-3)² - 4 · 1 · (-4)
Δ = 9 + 16
Δ = 25

x = -b +- √Δ / 2*a
x' = $\frac{3 + 5}{2 * 1} = \frac{8}{2} = 4$
x" = $\frac{3 - 5}{2 * 1} = \frac{-2}{2} = -1$


b) x² + 8x + 16 = 0
Δ = b² - 4 · a · c
Δ = 8² - 4 · 1 · 16
Δ = 64 - 64
Δ = 0

x = -b +- √Δ / 2*a
x' = $\frac{8 + 0}{2 * 1} = \frac{8}{2} = 4$
x" = $\frac{8 - 0}{2 * 1} = \frac{8}{2} = 4$
x' = x" = 4

c) 3² - 2x - 1 = 0
9 - 2x - 1 = 0
2x + 8 = 0
2x = -8
x = $\frac{-8}{2}$
x = -4