Question

1) Resolva as equações do 1o grau abaixo, utilizando o método prático:

a) 4x + 18 = 2x + 28 f) 7x – 3x = 70 – 30

b) 25x = 50 g) 9y – 25 + y = 32 + 3y – 1

c) 50x = 25 h) 29 + 13b + 5b = 11

d) 3x = 40 + 2x – 7 + 5x – 22

i) x + x + x + 30 = 2x + 3x + 4x

e) 23 – 8y – 15 = – 2y + 26

j) 7a + 35 – 2a – 19 = 5a + 26 – 4a + 20 – 6a

Answer 1

Resposta:

a) 4x + 18 = 2x + 28

$4x + 18 - 2x - 28 = 0 \\ 2x - 10 = 0 \div 2 \\ x - 5 = 0 \\ x = 5$

b) 25x = 50

$25x = 50 \div 25 \\ x = 2$

c) 50x = 25

$50x = 25 \div 25 \\ 2x = 1 \\ \\ x = \frac{1}{2}$

d) 3x = 40 + 2x – 7 + 5x – 22

$3x - 40 - 2x + 7 - 5x + 22 = 0 \\ - 4x - 33 + 22 = 0 \\ - 4x - 11 = 0 \\ - 4x = 11 \times ( - 1) \\ 4x = - 11 \\ \\ x = - \frac{11}{4}$

e) 23 – 8y – 15 = – 2y + 26

$23 - 8y - 15 + 2y - 26 = 0 \\ - 18 - 6y = 0 \div 6 \\ - 3 - y = 0 \\ - y = 3 \times ( - 1) \\ y = - 3$

f) 7x – 3x = 70 – 30

$7x - 3x - 70 + 30 = 0 \\ 4x - 40 = 0 \\ 4x = 40 \div 4 \\ x = 10$

g) 9y – 25 + y = 32 + 3y – 1

$9y - 25 + y - 32 - 3y + 1 = 0 \\ 7y - 56 = 0 \\ 7y = 56 \\ \\ y = \frac{56}{7} \\ y = 8$

h) 29 + 13b + 5b = 11

$29 + 13b + 5b - 11 = 0 \\ 18 + 18b = 0 \\ 18b = - 18 \div 18 \\ b = - 1$

i) x + x + x + 30 = 2x + 3x + 4x

$3x + 30 - 2x - 3x - 4x = 0 \\ - 6x + 30 = 0 \\ - 6x = - 30 \times ( - 1) \\ 6x = 30 \div 6 \\ x = 5$

j) 7a + 35 – 2a – 19 = 5a + 26 – 4a + 20 – 6a

$5a + 16 = a - 6a + 46 \\ 5a + 16 - a + 6a - 46 = 0 \\ 10a - 30 = 0 \\ 10a = 30 \div 10 \\ a = 3$