Saturday, 29 April 2017

LOGARITHMS 21


Find x if Log4x + Log4(3x+8) =2

Solution

Log4x + Log4(3x+8) =2
Log4x(3x+8) =2
x(3x+8) =42
3x2+ 8x =42.
3x2+ 8x =16.
3x2+ 8x - 16=0
3x2+ 12x – 4x- 16=0       [Splitting +8x into 12x – 4x]
(3x2+ 12x) – (4x+16)=0     [grouping the factors] 
3x(x+ 4) – 4(x+ 4)=0     [taking out common factors] 
(3x- 4)(x+4)=0    
3x- 4=0 OR x+4=0    
3x = 4 OR x = -4
3x = 4 OR x = -4
3      3
x = 4/3 OR x = -4

Hence x = 4/3 OR x = -4

TRY THIS…………………………  


Find m if Log9m + Log9(m-24) =0

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