Maths - logarithmic equations

👨🏻‍🏫 學術台數學

Lan

2009-04-19 4:46 am

Please help me solve the equation as shown as below.

Q. log(base4) (x+3) + log(base4) (x-3) = 2

回答 (2)

用戶7639

2009-04-19 6:44 am

✔ 最佳答案

log4 (x+3) + log4(x-3) = 2
log4[(x+3)(x-3)]=2
(x+3)(x-3)=42
x2-9=16
x2=25
x=5或x=-5(rejected.)

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用戶10012

2009-04-19 4:55 am

2 = log(base4)16, so the equation becomes
log(x +3) + log(x -3) = log16
(x+3)(x-3) = 16
x^2 - 9 = 16
x^2 = 25
x = 5.

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