Question

8x+8=(x+1)e^(5x+10) solve for x. I can get one answer that is correct =-1.584112, but there is another answer of -1. I do not know how to get the second answer.

Answer 1

Well, look at it this way: What happens when you plug in -1?

Answer 2

-1 is the easy one. get 0 = 0
how did you get the other one?

Answer 3

I factored out the 8 on the left side. then divided by (x+1). then took the ln of both sides

Answer 4

ln(8)=5x+10 Then solved for x.
but I still do not understand the -1 answer

Answer 5

ok that works, but not if x = -1 because you divided by x+1

Answer 6

so of course if you divide both sides by x + 1 you are tacitly assuming that x is not -1, so cannot get that answer using that method

Answer 7

you get x = -1 "by inspection" namely by noting that if x = -1 both the left and right hand side are 0.

Answer 8

ok, I understand a little better. Thank you!