Question 607150
  <pre><font face = "Tohoma" size = 4 color = "indigo"><b> 
Hi,
log x+log(x+21)=2
log x(x+21) = 2
  10^2 = x^2 + 21x
     x^2 + 21x-100 = 0
Factoring***
   (x+25(x-4) = 0
   (x+25) = 0, x = {{{highlight(cross(-25))}}}
    (x-4) = 0, x = 4
Using FOIL to check our Factoring***
F	First terms    x^2
O	Outside terms  -4x
I	Inside terms   +25x 
L	Last terms     -100