In(y+9)+In(y-9)=3

Question

Help me 

Answer 1

This is a sum of logs.  According to the properties of logarithms, this can rewritten as a product.

 

ln((y + 9)(y - 9)) = 3

 

 

The solution to a natural log is the exponent of the base number e.  We only use the base number 10 when we have log.

 

(y + 9)(y - 9) = e³

y² - 81 = e³

y² = e³ + 81

 

y= √(e³ + 81)

 

y = 10.054