Question

log3 (x + 1) + log3 (x - 7) = 2

Answer 1

log3 (x + 1) + log3 (x - 7) = 2

log3 (x + 1)•(x - 7) = 2

(x + 1)•(x - 7) = 3²

x² -6x -7 = 9

x² -6x -16 = 0

∆=36+64=100 => √∆=10

x' = -b+√∆/2a = 6+10/2= 16/2 = 8 ✓