+128707 -2log8(x + 1) = -8
It's a little difficult to tell what you're using as the base ....if it's 10, we have this
Let's divide both sides by -2 This gives
log8(x + 1) = 4
Writing in exponential form, we have
10^4 = 8 (x + 1) Therefore
10,000 = 8(x + 1) Now, divide both sides by 8 This gives
1250 = x +1 Subtracting 1 from both sides gives us
x = 1249
However, if you're using 8 as the base, let's take it from this point
log8(x + 1) = 4
Now, let's write this in exponential form using base 8......we have
8^4 = x +1
4096 = x + 1 And subtracting 1 from each side gives us
x = 4095
I suspect that the second thing might be what you meant, but anyway, you have answers using both bases!!! 
+128707 -2log8(x + 1) = -8
It's a little difficult to tell what you're using as the base ....if it's 10, we have this
Let's divide both sides by -2 This gives
log8(x + 1) = 4
Writing in exponential form, we have
10^4 = 8 (x + 1) Therefore
10,000 = 8(x + 1) Now, divide both sides by 8 This gives
1250 = x +1 Subtracting 1 from both sides gives us
x = 1249
However, if you're using 8 as the base, let's take it from this point
log8(x + 1) = 4
Now, let's write this in exponential form using base 8......we have
8^4 = x +1
4096 = x + 1 And subtracting 1 from each side gives us
x = 4095
I suspect that the second thing might be what you meant, but anyway, you have answers using both bases!!!
