Question

calcule o valor das incógnitas

a) 18 x + 43 = 61

d) x/4 -2= 1/4

c) 0,8 + 2x = 3,8

b) 2x² + 8x =0

e) x² -8 x + 7 = 0

f) x² -3 x - 4 = 0​

Answer 1

RESPOSTA:

a) x = 1

b) x = 9

c) x = 1,5

d) x = -4

e) S = {7, 1}

f) S = {4, -1}

RESOLUÇÃO:

a)

18x + 43 = 61

18x = 18

x = 18/18

x = 1

b)

x/4 - 2 = 1/4

x/4 = 9/4

x = 4 × 9/4

x = 36/4

x = 9

c)

0,8 + 2x = 3,8

2x = 3

x = 3/2

x = 1,5

d)

2x² + 8x = 0

x (2x + 8) = 0

2x + 8 = 0

2x = -8

x = -4

e)

x² - 8x + 7 = 0

∆ = b² -4ac

∆ = (-8)² - 4 × 1 × 7

∆ = 64 - 28

∆ = 36

x = -b ± √∆/2a

x = 8 ± √36/2

x1 = 8 + 6/2

x1 = 14/2

x1 = 7

x2 = 8 - 6/2

x2 = 2/2

x2 = 1

f)

x² - 3x - 4 = 0

∆ = b² - 4ac

∆ = (-3)² - 4 × 1 × (-4)

∆ = 9 + 16

∆ = 25

x = -b ± √∆/2

x = 3 ± √25/2

x1 = 3 + 5/2

x1 = 8/2

x1 = 4

x2 = 3 - 5/2

x2 = -2/2

x2 = -1

Espero ajudar.