Question

Calcule o valor de x. a) x/3= 3/2 b)4x/5 = x+1/3 c) 2-x/x+5 = 3/4 d) x/2 = x²/7?

Answer 1

Calcule o valor de x.
 a) x/3= 3/2

x         3
--- = -------  ( só cruzar)
3         2

2(x) = 3(3)
2x = 9
x = 9/2


 b)4x/5 = x+1/3

4x       x + 1
----- = ----------
  5         3

3(4x) = 5(x + 1)
12x = 5x + 5
12x - 5x = 5
7x = 5
x = 5/7


c) 2-x/x+5 = 3/4

2 - x         3
------- = --------
x + 5        4

3(x + 5) = 4(2 - x)
3x + 15 = 8 - 4x
3x + 15 + 4x = 8
3x + 4x = 8 - 15
7x = - 7
x = - 7/7
x = - 1


d) x/2 = x²/7?

x         x²
---- = -------
2         7

2(x²) = 7(x)
2x² = 7x
2x² - 7x = 0
x(2x - 7) = 0

x = 0

(2x - 7) = 0
2x - 7 = 0
2x = + 7
x = 7/2

assim
x = 0
x = 7/2