一題對數方程問題

log₄(x+4)+log₄(x+10)=2
log₄[(x+4)(x+10)]=log₄(4²)
(x+4)(x+10)=(4²)
x²+14x+40=16
x²+14x+24=0
(x+2)(x+12)=0
x=-2 or x=-12(rej.)
(rejected -12 because log₄[(-12)+4] = log₄(-8) and log can not be negative)