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Mathematics 11 Online
OpenStudy (anonymous):

need to find the solution to this equation.

OpenStudy (anonymous):

\[y ^{-1}-22y -_{2}^{1}+12-=0\]

OpenStudy (anonymous):

I couldn't get this to look right. it is supposed to be y with the -1/2 as the square root

OpenStudy (anonymous):

Is it \[{1 \over y}-22y^{-1/2}+12=0?\]

myininaya (myininaya):

let u=y^(-1/2) so we have u^2=y^(-1)

myininaya (myininaya):

u^2-22u+12=0

OpenStudy (anonymous):

I got 12 and 10. is that correct?

OpenStudy (anonymous):

or maybe they are negative?

myininaya (myininaya):

one sec im scanning something

OpenStudy (anonymous):

ok, thanks

myininaya (myininaya):

OpenStudy (anonymous):

wow, thanks for doing that! I can see where I maybe slipped up. I am a bit confused as to what the answer is though. Is there still one more step in solving those 2 solutions?

myininaya (myininaya):

i didn't simplify

OpenStudy (anonymous):

for some reason i'm not getting a whole number

myininaya (myininaya):

i'm not getting a whole number

OpenStudy (anonymous):

i just realized that you had 12 in the problem when it's supposed to be 120. Sorry if I typed it wrong.

OpenStudy (anonymous):

yep, I did... ahh. sorry.

myininaya (myininaya):

lol. okay lets take another look at it

OpenStudy (anonymous):

Thanks! :)

myininaya (myininaya):

so we get u=10 and u=12 like you been talking about this whole time but u=y^(-1/2) y^(-1/2)=10 and y^(-1/2)=12 so y=10^(-2)=1/(10^2)=1/100 so y=12^(-2)=1/(12^2)=1/144 there you basically had it you just needed to solve for y

myininaya (myininaya):

we got u=12 and 10 because u^2-22u+120=(u-12)*(u-10)=0 so very good

OpenStudy (anonymous):

ok I just wasn't sure if they were supposed to stay positive.

OpenStudy (anonymous):

Thanks for clarifying!

myininaya (myininaya):

to get rid of that -1/2 exponent i just raised both sides to -2 because law of exponents tells me if we have (x^{-1/2)^{-2} to multiply the exponents but if i do this to one side i have to do it to the other

OpenStudy (anonymous):

okk got it:)

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