solve the following equations.
1 ) log(x-3) +log (x-5) =1
2) log (x^2+4)- 2logx =1
3) log(4+x)+log (4-x) =log7
Log. equations?
2016-09-28 12:56 pm
回答 (2)
2016-09-28 3:27 pm
solve the following equations.
1 ) log(x－3) +log (x－5) =1
(x－3)(x－5)=10
x^2－8x+15=10
x^2－8x+5=0
x=(8+√(64-20)/2 (負不合)
=4+√11
2) log (x^2+4)－2logx =1
log(x^2+4)=1+logx^2
x^2+4=10x^2
x^2=4/9
x=2/3 or x=－2/3(不合)
3) log(4+x)+log (4－x) =log7
log[4+x)(4－x)]=log7
16－x^2=7
x^2=9
x=3 or x=－3(不合)
1 ) log(x－3) +log (x－5) =1
(x－3)(x－5)=10
x^2－8x+15=10
x^2－8x+5=0
x=(8+√(64-20)/2 (負不合)
=4+√11
2) log (x^2+4)－2logx =1
log(x^2+4)=1+logx^2
x^2+4=10x^2
x^2=4/9
x=2/3 or x=－2/3(不合)
3) log(4+x)+log (4－x) =log7
log[4+x)(4－x)]=log7
16－x^2=7
x^2=9
x=3 or x=－3(不合)
2016-09-28 1:57 pm
1)=根號11+4
收錄日期: 2021-04-30 21:53:46
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