Respostas

2014-06-02T15:50:15-03:00
A) x/2 - 4/x = 1
x² - 8 - 2x = 0
Δ = -2² -4.1.-8
Δ = 4 + 32
Δ = 36
x = 2 +- 6/2.1
x1 = 6
x2 = -2

B)4 - x = 5/x
4x- x² = 5
-x² + 4x -5 = 0 (-1)
x² - 4x + 5 = 0
Δ = -4² -4.1.5
Δ = 16 - 20
Δ = -4
x = Ф

C) 5/x² = 4 + 3/x
 5 = 4x² + 3x
4x² + 3x - 5 = 0
Δ = 3² -4.4.-5
Δ = 89
x = - 3 +- 9,43/ 8
x1 = 0,803
x2 = -1,55

D) x = 21/x - 20
x² = 21 - 20x
x² + 20x - 21 = 0
Δ = 20² -4.1.-21
Δ = 400 + 84
Δ = 484
x = - 20 +- 22/2
x1 = -21
x2 = 1