Resposta:

Olá!

5)

a)

[tex](2+7) \sqrt{3} = 9\sqrt{3}[/tex]

b)

[tex]3\sqrt{5}-2\sqrt{5}+\sqrt{5}+4-8[/tex]

[tex](3-2+1)\sqrt{5}-4[/tex]

[tex]2\sqrt{5}-4[/tex]

6)

a)

[tex]\sqrt{2}*\sqrt{5} = \sqrt{2*5} = \sqrt{10}[/tex]

b)

[tex]\sqrt{2*8} = \sqrt{16} = 4[/tex]

7)

a)

15x = 5(24)

15x = 120

x = 120 / 15

x = 8

b)

(55 - x)4 = 3(6)

220 - 4x = 18

-4x = 18 - 220

-4x = -202   .(-1)

4x = 202

x = 202/4

x = 101/2

x = 50,5

8)

x + y = 11

2x - 4y = 10  :(2)

x + y = 11

x - 2y = 5

_________

x = 11 - y

11 - y - 2y = 5

11 - 3y = 5

-3y = 5 - 11   .(-1)

3y = 11 - 5

3y = 6

y = 2

x = 11 - 2

x = 9

S = {9 , 2}