Respostas

A melhor resposta!
2014-04-21T13:29:43-03:00
X(x + 3) - 40 = 0

x(x + 3) = 40 (aplicando a distributiva)

x² + 3x = 40 (igualar a 0 e aplicar báskara para resolver)

x² + 3x - 40 = 0

Δ = b² - 4ac
Δ = 3² - 4.1.(-40)
Δ = 9 + 160
Δ = 169

x = x =  \frac{-3+ \sqrt{169}}{2} 
\\
x =  \frac{-3+13}{2} 
\\ x =  \frac{10}{2}
\\ x = 5 \\ e \\ x =  \frac{- 3 - 13}{2} \\ x = \frac{-16}{2} \\    x = - 8

S = { 5; - 8}

Espero ter ajudado.
6 4 6
2014-04-21T13:31:38-03:00
X(x+3)-40=0
x²+3x-40
Δ=b²-4ac
Δ=3²-4·1·(-40)
Δ=9+160
Δ=169

x=-b+-√Δ / 2a
x=-3+-13 / 2a
x'= -3+13 / 2 = 10/2= 5
x''= -3-13 / 2 = -16/2= -8 
4 4 4