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DF001
 one year ago
Help with an Algebra II question!
(Subtracting fractions with unlike denominator.)
DF001
 one year ago
Help with an Algebra II question! (Subtracting fractions with unlike denominator.)

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DF001
 one year ago
Best ResponseYou've already chosen the best response.1\[\frac{ S1 }{ S }  \frac{ T+1 }{ T }\]

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2what's the LCD in this case?

DF001
 one year ago
Best ResponseYou've already chosen the best response.1I have trouble figuring out the LCD, I was never good at it. Please teach me :(

DF001
 one year ago
Best ResponseYou've already chosen the best response.1I thought you multiple the fractions by the opposite denominators

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2the denominators are S and T they have nothing in common except for 1, so we can multiply them to get the LCD the LCD is simply `ST` or `TS`

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2to add or subtract fractions, the denominators must be the same. They aren't in this case, so we have to get them all equal to the LCD

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2the first denominator is S we want it to be equal to ST or TS it's missing a T, so multiply top and bottom of the first fraction by T \[\Large \frac{ S1 }{ S }  \frac{ T+1 }{ T }\] \[\Large \frac{\color{red}{T}}{\color{red}{T}}\times\frac{ S1 }{ S }  \frac{ T+1 }{ T }\] \[\Large \frac{ \color{red}{T}(S1) }{ \color{red}{T}S }  \frac{ T+1 }{ T }\]

DF001
 one year ago
Best ResponseYou've already chosen the best response.1If in other cases like one denominator is 3a+12 and the other is a+4, how can I find the LCD in this?

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2notice how the `T/T` is a fancy form of 1. Multiplying by 1 doesn't change the fraction

DF001
 one year ago
Best ResponseYou've already chosen the best response.1As to why do we want it to equal ST or TS?

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2you would factor 3a+12 to get 3(a+4) we really have the denominators 3(a+4) and a+4 so the LCD is 3(a+4). The unique factors are 3 and (a+4)

DF001
 one year ago
Best ResponseYou've already chosen the best response.1Can I get a brief definition of what an lcd is

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2LCD = lowest common denominator it's the LCM of the denominators

DF001
 one year ago
Best ResponseYou've already chosen the best response.1Im not sure what it really means but, i thought it was the lowest number that can go into two numbers

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2for example 1/2 + 2/3 the LCD is 6 since the LCM of 2 and 3 is 6

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.26 is the lowest multiple both 2 and 3 have in common

DF001
 one year ago
Best ResponseYou've already chosen the best response.1Did you add the denominators together in 1/2+2/3

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2list the multiples of 2 2, 4, 6, 8, 10, 12, ... list the multiples of 3 3, 6, 9, 12, 15, 18, ... the common multiples are 6, 12, 18, ... the number 6 is the smallest multiple

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2so 6 is the LCM (lowest common multiple)

DF001
 one year ago
Best ResponseYou've already chosen the best response.1Back to the image 5 minutes ago, must you look at the first fraction first to know what to times the numerator and denominator by?

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2you mean back with the one with S and T in it?

DF001
 one year ago
Best ResponseYou've already chosen the best response.1I see the first fraction is times by T thus ST

DF001
 one year ago
Best ResponseYou've already chosen the best response.1But, if I do that to the first fraction, should I do that to the second fraction ?

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2you'll do something similar, but with S instead

DF001
 one year ago
Best ResponseYou've already chosen the best response.1thus, they have the same denominator ST

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2you'll multiply top and bottom of the second fraction by S

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2yes that's the ultimate goal: to get the denominators equal to the LCD (so they are all the same)

DF001
 one year ago
Best ResponseYou've already chosen the best response.1Oh, The answer I got for the ST question is 1T+1S/ST

DF001
 one year ago
Best ResponseYou've already chosen the best response.1If I am correct about the numerator

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2so we have this so far after getting each denominator equal to the LCD \[\Large \frac{ S1 }{ S }  \frac{ T+1 }{ T }\] \[\Large \frac{\color{red}{T}}{\color{red}{T}}\times\frac{ S1 }{ S }  \frac{ T+1 }{ T }\] \[\Large \frac{ \color{red}{T}(S1) }{ \color{red}{T}S }  \frac{ T+1 }{ T }\] \[\Large \frac{ T(S1) }{ TS }  \frac{\color{red}{S}}{\color{red}{S}}\times\frac{ T+1 }{ T }\] \[\Large \frac{ T(S1) }{ TS }  \frac{ \color{red}{S}(T+1) }{ \color{red}{S}T }\] \[\Large \frac{ T(S1) }{ TS }  \frac{ S(T+1) }{ TS }\] agreed?

DF001
 one year ago
Best ResponseYou've already chosen the best response.1Yes but, I mines is T(S1)S(T+1)/TS

DF001
 one year ago
Best ResponseYou've already chosen the best response.1im not sure if thats the same as the last step

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2yeah you'll have T(S1)S(T+1) all over TS as one of your steps

DF001
 one year ago
Best ResponseYou've already chosen the best response.1I combined the denominator

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2\[\Large \frac{ T(S1) }{ TS }  \frac{ S(T+1) }{ TS }\] turns into \[\Large \frac{ T(S1)  S(T+1) }{ TS }\]

DF001
 one year ago
Best ResponseYou've already chosen the best response.1If I multiply t and s into what's in the parenthesis do I get \[\frac{ 1t+1s }{ st }\]

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2good, which is equivalent to \[\Large \frac{ST}{ST}\]

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2the TS terms up in the numerator will cancel (since 1TS  1TS = 0TS = 0)

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2oh wait, that S should be negative

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2\[\Large \frac{ T(S1)  S(T+1) }{ TS }\] \[\Large \frac{ TST  STS }{ TS }\] \[\Large \frac{ T S }{ TS }\]

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.2hopefully all that makes sense?

DF001
 one year ago
Best ResponseYou've already chosen the best response.1I got confused by the S
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