log maths question 1

👨🏻‍🏫 學術台數學

[匿名]

2011-10-27 3:16 am

please answer it in full sentence
1. log x + log(x-2) = log 8

回答 (2)

用戶27207

2011-10-27 3:24 am

✔ 最佳答案

1) logx+log(x-2)=log 8log[x(x-2)]=log8x(x-2)=8x²-2x-8=0 x-4)(x+2)=0So, x-4=0or x+2=0x=4 or x=-2(rej.)

參考: Hope I Can Help You ! ^_^ ( From Me )

👍 0 👎 0

數學人

2011-10-27 5:45 am

log x + log (x-2) = log 8
log [x(x-2)] = log 8
x^2 - 2x - 8 = 0
(x-4)(x+2) = 0
x=4 or x=-2 (rejected)
So x=4.

參考: own knowledge

👍 0 👎 0