Question

-2log8(a+1)=-8

Answer 1

change to exponential

log_8 (a+1)^-2 = -8

8^-8 = (a+1)^-2

raise both sides to -1/2 (to cancel -2 in the exponent of te right hand side)

8^4 = a+1

use calculator to find 8^4 - 1 that's your a

Answer 2

-2log8(a+1)=-8
log8(a+1) = 4
=> a + 1 = 8^4
=> a = 8^4 -1 = 4095