log9(x-5)+log9(x=+3)=1 9是那个log的底
问题描述:
log9(x-5)+log9(x=+3)=1 9是那个log的底
答
log9(x-5)(x+3)=log9(9)
x²-2x-15=9
x²-2x-24=0
(x-6)(x+4)=0
真数大于0
x-5>0,x+3>0
所以x=6