Respostas

2013-11-12T16:47:25-02:00
X^2-x-20=0  ( Fórmula de Bhaskara)
Δ = b² -4ac
Δ = (-1)² -4 *1 * (-20)
Δ = 1 + 80
Δ = 81
x' = (-b + √∆)/ 2a
(-(-1) + 9)/2 * 1
(1 + 9)/2
10/2
5
x'' = (-b - √∆)/ 2a
(-(-1) - 9)/2 * 1
(1 - 9)/2
-8/2
-4



x^2-3x-4= 0
Δ = b² -4ac
Δ = (-3)² -4 *1 * (-4)
Δ = 9 + 16
Δ = 25
x' = (-b + √∆)/ 2a
(-(-3) + 5)/2 * 1
(3 + 5)/2
8/2
4
x'' = (-b - √∆)/ 2a
(-(-3) - 5)/2 * 1
(3 - 5)/2
-2/2
-1

x^2-8x+7=0
Δ = b² -4ac
Δ = (-8)² -4 *1 * 7
Δ = 64 -28
Δ = 36
x' = (-b + √∆)/ 2a
(-(-8) + 6)/2 * 1
(8 + 6)/2
14/2
7
x'' = (-b - √∆)/ 2a
(-(-8) - 6)/2 * 1
(8 - 6)/2
2/2
1





2013-11-12T16:50:17-02:00
A)x1=5 ex2=-4
b)x1=4 e x2=-1
c) x1=7 e x2= 1