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Mathematics 7 Online
OpenStudy (dawnr):

Anyone?

OpenStudy (dawnr):

ganeshie8 (ganeshie8):

simplify using log properties ?

ganeshie8 (ganeshie8):

\[\large a \ln b = \ln b^a\] \[\large \ln a - \ln b = \ln\left(\dfrac{a}{b}\right)\]

OpenStudy (dawnr):

i need a set of solutions for this inequality i know those..but i get stuck at some point

ganeshie8 (ganeshie8):

where exactly you got stuck

OpenStudy (dawnr):

so i did this: 2ln(1-x)-ln(2x+6)<=0 2ln(1-x)/ln(2x+6)<=0 2ln(1-x)<= 0 and 2ln(2x+6)>=0 and idk what to do with this anymore xD

ganeshie8 (ganeshie8):

lets work it step by step

OpenStudy (dawnr):

lets :D

ganeshie8 (ganeshie8):

\[\large 2 \ln(1-x) - \ln (2x+6) \le 0\]

ganeshie8 (ganeshie8):

step 1 : for the first term, use the log property \(\large a \ln b = \ln b^a\) \[\large \ln(1-x)^2 - \ln (2x+6) \le 0\]

OpenStudy (dawnr):

okay..

ganeshie8 (ganeshie8):

next use the second log property \[\large \ln \left(\dfrac{(1-x)^2}{ (2x+6)} \right)\le 0\]

ganeshie8 (ganeshie8):

still wid me ? :)

OpenStudy (dawnr):

yup

ganeshie8 (ganeshie8):

next change it to exponent form using below : \(\ln a = b \) means \(a = e^b\)

ganeshie8 (ganeshie8):

\[\large \ln \left(\dfrac{(1-x)^2}{ (2x+6)} \right)\le 0\] \[\large \dfrac{(1-x)^2}{ (2x+6)} \le e^0\] \[\large \dfrac{(1-x)^2}{ (2x+6)} \le 1\] \[\large (1+x)^2 \le 2x+6\]

ganeshie8 (ganeshie8):

see if you can solve that inequality ^

ganeshie8 (ganeshie8):

\[\large (1\color{Red}{-}x)^2 \le 2x+6 ~~^*\]

OpenStudy (dawnr):

so i have x^2-4x-5<=0 and then i just do it like a normal equation right? :D

ganeshie8 (ganeshie8):

yes factor it first

OpenStudy (dawnr):

english is my 3rd language so i'm not quite sure what that means >_<

ganeshie8 (ganeshie8):

can you factor the quadratic ?

ganeshie8 (ganeshie8):

x^2-4x-5<=0 (x )(x )<=0

OpenStudy (dawnr):

right right i do xD we just do that differently

OpenStudy (dawnr):

x1/2=... thing :D

ganeshie8 (ganeshie8):

ohkay, what do u get after u factor it ? :)

OpenStudy (dawnr):

5 and -1

ganeshie8 (ganeshie8):

since the leading coefficient is positive, the graph between these zeroes stays negative, so the solutions will be : -1 <= x <= 5

ganeshie8 (ganeshie8):

however, from the first term of given given equation, x must be less than 1 (why ? )

OpenStudy (dawnr):

but it says here that the correct answer is [-1,1) :/

ganeshie8 (ganeshie8):

so the final solutions will be : -1 <= x < 1

OpenStudy (dawnr):

(1−x)2/(2x+6)≤1 because of this or..

ganeshie8 (ganeshie8):

\[\large 2 \color{red}{\ln(1-x) }- \ln (2x+6) \le 0\]

ganeshie8 (ganeshie8):

that part ^

ganeshie8 (ganeshie8):

since log cannot suck in negative values or 0 : 1-x > 0 x < 1

OpenStudy (dawnr):

got it! thank you :)

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