log9(x+5）为什么可以化简为½log3 x+5?

(log2^3 +log3^5) x ( log3^5 +log9^5 ) x lg 2 , 由换底公式怎么得到log9(x+5)=log3[2（x+5)]=1/2log3(x+5) 填空题：方程log3(x-1)=log9(x+5)的解是____________ log3(5)+log9(5)求大神帮助 log3 5-log3 15+1/2log9 27 的值 (log2(3)+log8(9))x(log3(4)+log9(8)+log3(2)) 求x,y值.6log9^x+3log27^y=8log3^x+2log9^y=2 -5log9为底4的对数+log3为底(32/9)的对数-5^(log5为底3的对数)-（1/64）^(-2/3) 解不等式:log3^(5+x)+log3^(x-1)≤3 log9(45)-log9(5) log 243÷log9 =log3^5÷log3^2 =log3^5-log3^2 然后怎么写 若log2^3×log3^4×log4^x=log9^3 ,求x