Mathematics
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OpenStudy (toxicsugar22):
can someone help me with this question log(x+3)+log (x)=1
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OpenStudy (toxicsugar22):
sorry
OpenStudy (anonymous):
base 10?
OpenStudy (anonymous):
yes
OpenStudy (toxicsugar22):
log(x+3)+logx=1
OpenStudy (anonymous):
log[(x+3)*(x)]=1
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OpenStudy (anonymous):
oh yeah. rewrite as one log
\[log(x(x+3)) = 1\] so \[log(x^2+3x)=1\] then rewrite in equivalent experiential form
\[x^2+3x=10^1\]
OpenStudy (anonymous):
now you have a quadratic to solve
\[x^2+3x-10=0\]
\[(x+5)(x-2)=0\]
\[x+5=0\]
\[x=-5\] or \[x-2=0\] \[x=2\]
OpenStudy (amistre64):
5 and 2 i think are better options ;)
OpenStudy (anonymous):
but you cannot take the log of a negative number so answer is 2
OpenStudy (anonymous):
no i like my answers. it does factor as
\[(x+5)(x-2)\] right?
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OpenStudy (anonymous):
yeah
OpenStudy (toxicsugar22):
ok thanks i got that
OpenStudy (anonymous):
whew so answer is 2
OpenStudy (anonymous):
don't put -5!
OpenStudy (anonymous):
yeah
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OpenStudy (toxicsugar22):
i didnt
OpenStudy (amistre64):
5 and 2 are better options for the factoring than 5 and 3 :)
OpenStudy (toxicsugar22):
can u help me with this one to
OpenStudy (anonymous):
did i put 5 and 3?
OpenStudy (amistre64):
....no, the deleted post did tho
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OpenStudy (anonymous):
no i did
OpenStudy (anonymous):
oh...
OpenStudy (anonymous):
you are paying too close attention!
OpenStudy (amistre64):
lol
OpenStudy (amistre64):
just trying to keep my mind of the money pit im driving in
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OpenStudy (toxicsugar22):
so it is 2
OpenStudy (toxicsugar22):
the answer is 2
OpenStudy (toxicsugar22):
is it
OpenStudy (anonymous):
yes 2
OpenStudy (toxicsugar22):
and not -5
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OpenStudy (anonymous):
because \[log(5)+log(2)=log(10)=1\]
OpenStudy (anonymous):
you cannot take the log of a negative number
OpenStudy (toxicsugar22):
ok
OpenStudy (anonymous):
if i write \[log(-5)=x\] that means
\[10^x=-5\] but
\[10^x\] is always positive so it cannot be -5
OpenStudy (toxicsugar22):
ok thanks
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OpenStudy (anonymous):
welcome