Question

Dos números 3, -1 e 5 , quais são raízes de x²-2x-3=0 ?

Answer 1

x²-2x-3=0
a=1; b=-2; c=-3
∆=b²-4ac⇒ ∆=(-2)²-4.1.(-3)⇒ ∆=4+12⇒ ∆=16
x=-b±√∆ / 2.a⇒ x=-(-2)± √16 / 2.1⇒ x=2±4 / 2
x'=2+4/2⇒ x'=6/2⇒ x'=3
x''=2-4/2⇒ x''=-2/2⇒ x''=-1
S={-1 , 3}

As raízes são  -1 e 3.

Answer 2

$x^2-2x-3=0 \\ \\ \\ D=(-2)^2-4.1.(-3) \\ \\ D=4+12 \\ \\ D=16 \\ \\ \\ x'= \frac{-(-2)+ \sqrt{16} }{2.1} \>\>\>\>\>\>x'= \frac{2+4}{2} \>\>\>\>\>\>x'=3 \\ \\ x"= \frac{-(-2)- \sqrt{16} }{2.1} \>\>\>\>\>\>x"= \frac{2-4}{2} \>\>\>\>\>\>x"=-1$