Wednesday, 5 July 2017

LOGARITHMS 6

If Log[(30x-70)/(5+x)] = 1. Find x.

Solution

Log[(30x-70)/(5+x)] = 1.

Log10[(30x-70)/(5+x)] = 1.

 30x-70 = 101. After changing into exponential form
   5+x

30x-70 = 10    since [101=10]
   5+x

30x-70 = 10(5+x)    after cross multiply
  
30x-70 = 50+10x

30x-10x = 50+70 [collecting like terms]

20x = 120

x=6  [after dividing by 20 both sides]

Hence x=6.

TRY THIS……………


If Log[(2x+4)/(x-2)] = 1. Find x.


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