Mathematics
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OpenStudy (anonymous):
some one please teach me how to do these please? im so confused :c
simplify the expression x^2 + 6x + 9 / 5x + 15
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OpenStudy (jim766):
x^2 + 6x + 9 do you know how to factor this?
OpenStudy (jim766):
factoring means rewriting so it is 2 things mulitplied together
( ) ( ) what times what = x^2
OpenStudy (anonymous):
i have no clue...
OpenStudy (jim766):
(x + 3 )(x + 3) = x^2 + 6x + 9
------------ ------------
5x + 15 do you know the commond denominator
OpenStudy (jim766):
what divides evenly into both 5 and 15
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OpenStudy (anonymous):
3
OpenStudy (anonymous):
wait how did you get that equation?!?!
OpenStudy (jim766):
which one?
OpenStudy (anonymous):
(x + 3 )(x + 3) = x^2 + 6x + 9
------------ ------------
5x + 15
OpenStudy (jim766):
x^2 + 6x + 9 if we factor it, it will be (x + 3)(x + 3)
try it, do you know how to multiply (x+ 3)(x + 3)
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OpenStudy (anonymous):
um 3x and 3x? im sorry im so confused
OpenStudy (jim766):
ok lets start from the begining.
(x + 3)(x+ 3) have your heard of FOIL?
OpenStudy (anonymous):
ive heard of it.. but i dont how to use it
OpenStudy (jim766):
It tells us how to multiply to binomials
(x + 3) (x + 3 )
F irst O uter I nner L asts
x *x x * 3 3 * x 3 * 3 do you see where I got this?
OpenStudy (anonymous):
Ohhh i see! but i still dont get who you got the 3.. do you use 3 in every expression like this one?
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OpenStudy (anonymous):
how not who **
OpenStudy (jim766):
ok just lets finish this
F irst O uter I nner L asts
x *x x * 3 3 * x 3 * 3
x^2 + 3x + 3x + 9
x^2 + 6x + 9
OpenStudy (jim766):
x^2 + 6x + 9
now ,do you see how this is in your original problem?
OpenStudy (anonymous):
OHHHH yes! thank you! okay go on :)
OpenStudy (anonymous):
oh wait you factor the numberator
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OpenStudy (anonymous):
okay i got that part and then you factor the denominator which is....?
OpenStudy (jim766):
x^2 + 6x + 9
to factor this, I start off with what time what = x^2
x * x = x^2 , so I put it in the front
(x )(x )
OpenStudy (jim766):
x time x = x^2
OpenStudy (anonymous):
x * 3 and x* 3 ??
OpenStudy (jim766):
(x + 3)(x +3)
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OpenStudy (anonymous):
right right. sorry... go on! :)
OpenStudy (jim766):
now look at the denominator 5x + 15
what number divides evenly into both 5 and 15
(it is not 3)
OpenStudy (anonymous):
5 !
OpenStudy (jim766):
right, that is the common denominator....
OpenStudy (anonymous):
so the factors are ( x + 5) and ( x +5 ) ??
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OpenStudy (anonymous):
or just ( x + 3 ) ( x + 3 )
---------------
5
OpenStudy (jim766):
this one is a little different...
5x + 15 common denominator is 5
5( ) now divide everthing by 5
OpenStudy (jim766):
5x + 15 common denominator is 5
--- ---
5 5
5( x + 3) now divide everthing by 5
OpenStudy (jim766):
(x + 3 )(x + 3) = x^2 + 6x + 9
------------ ------------
5 (x + 3) 5x + 15
OpenStudy (jim766):
what can You cancel out?
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OpenStudy (anonymous):
the threes !
OpenStudy (jim766):
the (x +3)s
OpenStudy (anonymous):
yes
OpenStudy (jim766):
leaving you with x + 3
------
5
OpenStudy (anonymous):
thats the answer??
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OpenStudy (jim766):
you only can cancel one out so the other is left
OpenStudy (jim766):
yet that is the answer
OpenStudy (jim766):
* yep
OpenStudy (anonymous):
Ohhh i get it thank you sooooooo much! heres your medal :D
OpenStudy (jim766):
yw
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OpenStudy (anonymous):
can you help me with another one? i just need help going through it...
OpenStudy (jim766):
sure...
OpenStudy (anonymous):
okay its \[2x^2 - 4a +2 / 3a^2 - 3\]
OpenStudy (anonymous):
so i factor the numberator which is... (x-2) (x+2) ??
OpenStudy (jim766):
yes you have to factor the numerator...but start by looking for a GCF
What divides evenly into 2, -4 and 2
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OpenStudy (anonymous):
its -2 or 2
OpenStudy (jim766):
yes, usually we will keep it positive, so lets use 2
2a^2 -4a + 2
--- --- ---
2 2 2
2 (
OpenStudy (jim766):
what is 2a^2 divided by 2
OpenStudy (anonymous):
a^2 ??
OpenStudy (jim766):
\[\frac{ 2a^2 }{ 2 }\]
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OpenStudy (anonymous):
a squared
OpenStudy (jim766):
right, divide each of the terms by 2
OpenStudy (jim766):
2a^2 -4a + 2
2 (a^2 - 2a + 1) do you see where I got that?
OpenStudy (anonymous):
so its a^2 - 2a +1
OpenStudy (anonymous):
yes you divided 2 to every thing
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OpenStudy (anonymous):
by everything i mean the numberator numbers
OpenStudy (jim766):
ok now we have to factor that
2 (a^2 -2a + 1 )
2 (a )(a ) what 2 numbers mult to get 1 and add to get -2?
OpenStudy (anonymous):
-1 and -1
OpenStudy (jim766):
right that is what you put in the parentheses
2 (a - 1 )(a - 1 ) now that is factored
OpenStudy (anonymous):
ok
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OpenStudy (jim766):
now factor 3a^2 -3 what is the GCF?
OpenStudy (jim766):
what goes evenly into 3 and -3?
OpenStudy (anonymous):
1?
OpenStudy (jim766):
yes 1 does, but is it the biggest that goes evenly into both?
OpenStudy (anonymous):
3 !!!! duhh!! haha oops!
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OpenStudy (jim766):
right now divide everything by 3
3a^2 -3
-- --
3 3
3 (
OpenStudy (anonymous):
all thats left is a^2
OpenStudy (anonymous):
a^2 -1
OpenStudy (jim766):
right...
3 (a^2 - 1) this can still be factored though...
OpenStudy (jim766):
3 (a )( a )
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OpenStudy (jim766):
what 2 numbers can you mult together to get -1
OpenStudy (anonymous):
3 (a-1) ( a-1) ??
OpenStudy (jim766):
almost... -1* -1 = 1
OpenStudy (anonymous):
ohh ok i get i
OpenStudy (anonymous):
so its 3 (a +1) (a + 1)
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OpenStudy (jim766):
almost again -1 * +1 = -1
2 (a - 1 )(a - 1 )
---------------------- which cancels out?
3 (a +1) (a - 1)
OpenStudy (anonymous):
the ones cancel out so its just 2/3
OpenStudy (anonymous):
right?
OpenStudy (jim766):
anything divided by itself equal 1
(a-1)/(a-1) = 1
one (a -1) on top and one (a-1) on bottom cancels, whats left?
OpenStudy (anonymous):
2(a-1)
------
3 (a+1)
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OpenStudy (jim766):
thats right, thats the answer...
OpenStudy (anonymous):
THANKYOU so much for your help! im not going to fail! :D haha
OpenStudy (jim766):
keep working at it, youll get it!
OpenStudy (anonymous):
thanks!