Question

calcule o valor de x na proporção:

a) 2/5=(x+2)/(x+2)

b) 5/12=(x+5)/(x-5)

c) 3/6=(x+3)/(x-6)

d)2/4=(x+7)/(x-7)

Answer 1

a) X= -2
b) X= 85/7
c) X= -12
d) X= -21

Answer 2

a) 2 = (x+2)  ==> 5(x+2) = 2(x+2) ==> 5x+10=2x+4=> 5x-2x= 4-10=> 
    5    (x+2)

5x-2x= 4-10=> 3x = - 6 ==> x = - 2
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b) 5 = (x+5) => 12(x+5)=5(x-5) => 12x+60=5x-25=> 
   12   (x-5)

12x-5x = - 25-60 ==> 7x = - 85 ==> x = - 85/7
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c) 3 = (x+3) ==> 6(x+3)=3(x-6)=> 6x+18=3x-18
    6     x-6
6x-3x = - 18-18==. 3x = - 36 ==> x = - 12
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d) 2 =(x+7) ==> 4(x+7)=2(x-7) ==> 4x+28=2x-14
    4    x-7

4x-2x = -14-28 ==> 2x = - 42 ==> x = - 21