Question

calcule o valor de x nas proporções:
a)4/2x = 6/x+2 b)3,5/x+8 = 2,1/3x

Answer 1

a) $\frac{4}{2x} \ = \ \frac{6}{x+2}$

Multiplicamos meios pelos extremos:

4 . (x + 2) = 2x . 6
4x + 8 = 12x
12x - 4x = 8
8x = 8
x = 8/8

x = 1


b) Reescrevendo os numeradores:

3,5 = $\frac{7}{2}$

2,1 = $\frac{21}{10}$


$\frac{ \frac{7}{2} }{x+8} \ = \ \frac{ \frac{21}{10} }{3x}$

$\frac{7}{2} \ . \ \frac{1}{x+8} \ = \ \frac{21}{10} \ . \ \frac{1}{3x}$

$\frac{7}{2x+16} \ = \ \frac{21}{30x}$

Multiplicamos meios pelos extremos:

7 . 30x = (2x + 16) . 21
210x = 42x + 336
210x - 42x = 336
168x = 336
x = 336/168

x = 2