3x^2 +8x + 5
factoring trinomials
PLEASE HELP
 anonymous
3x^2 +8x + 5
factoring trinomials
PLEASE HELP
 Stacey Warren  Expert brainly.com
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 katieb
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 anonymous
alright, let's factor :
\[(3x + 5)(x + 1) = 0\]
use the FOIL method to check your answer ^_^
 anonymous
how do you figure them out so easy
 amistre64
skill and class :)
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 anonymous
exactly lol ^_^ , practice makes perfect :)
Believe me, I was so bad at these lol
 anonymous
class hasnt helped me lol
 anonymous
class won't help, it just introduces the concept, only you can help yourself :)
 amistre64
it helps when 3 and 5 make 8 right in front of you tho, but it takes practice to notice it ...
 amistre64
i use the first and last numbers, and the signs of the middle and last numbers to figure alot of it out....
 anonymous
i have the test tomarrow so we'l see
 amistre64
there are some underlying concepts to be aware of that help.... like how the equation is constructed to begine with and that way you can more easily tear it apart
 anonymous
so on this next one 5w^2 + 13w  6
 anonymous
you're going to do great ^_^
 amistre64
5(6) = 30... the last signis negative so the signs are different and its subtraction.... the middle number is positive so the largest factor is the positive...
 amistre64
(w+/5)(w/5) is my setup...
 amistre64
1,30; 2,15, 3,5 153=13 use it
 amistre64
(w+15/5)(w2/5) simplify and shift
 amistre64
(w+3)(5w2)
 anonymous
ok so what the first and last multipy out to the middle needs to add up to that number
 amistre64
want me to go slower :)
 anonymous
yes please
 amistre64
the first number is used to "calibrate" the rest. does that make sense?
 anonymous
yes
 amistre64
ok... the last number is used with the first number to find a "pool" of options for our middle number... does that make sense?
 anonymous
yea
 amistre64
5(6) = 30...what are our options...all of them...
 anonymous
the factors of 30
 amistre64
yes, what are they so we can see them :)
 amistre64
start with the obvious..1,30; and move on
 anonymous
15*2 6*5 30* 1
 amistre64
thats good, lets keep those available while we "setup" our answer
 amistre64
the last number is gotten by multiplication right? so the sign of that number tells us alot of what we need to use
 amistre64
if the sign is () what are our options?
 anonymous
152 ?
 amistre64
well get to that... but for now, focus on the sign only and not the value of the number...
our set up is this:
( w ) (w ) we need some signs....
 anonymous
one of each
 anonymous
plus and minus
 amistre64
good job.... now look at the middle number and that tells you which number is bigger... does that make sense?
 amistre64
whats the middle sign? + or ?
 anonymous

 amistre64
that middle number is +13 right?
 anonymous
yea
 amistre64
then we want our "bigger" numbe that we use to be (+)
(w + B )(w  L ) got it?
 amistre64
now which factor do we see that will subtract to get 13?
 anonymous
15 2
 amistre64
good
(w +15 )(w 2 )
couple more loose ends to wrap up
we used that "5" from the front to begin with and so we need to divide it out in this step like this:
(w +15/5 )(w 2/5 ) makes sense?
 anonymous
yes
 amistre64
simplify those fractions and if they still look like a fraction... move the bottom in front of its x partner like this:
(w +3 )(w 2/5 ) cant reduce anymore so move the denoms if there is any:
(w +3 )(5w 2) and were done
 anonymous
thank you so much our teacher goes to fast
 amistre64
lets do another one so I can see you do it :)
 anonymous
ok....2x^22x40
 amistre64
if it cant be done like this...use the quadratic formula :)
 amistre64
first step is what?
 anonymous
find the factors of 40?
 amistre64
close, first time last for a pool
 amistre64
2(40)
 amistre64
use that first now so we can divide it later... whats our pool?
 anonymous
oh ya...let me write this down
 amistre64
no writing...must do it the hard way :)
 anonymous
ok...80
 amistre64
write it down.... :)
 anonymous
i did lol
 amistre64
what are our "factors" of 80 to choose from?
 anonymous
2*40 8*10
 anonymous
80 *1
 amistre64
1,80; 2,40; 4, 10; 8, 5
 amistre64
8 and 10 lol forgot how to multiply
 amistre64
1,80; 2,40; 4,20; 8,10; 16; 5
thats better
 amistre64
lets start setup....
2x^22x40
(x )(x ) we need signs...what are they?
 anonymous
ok...both 
 amistre64
both () meaning? that ()()=()?
 anonymous
no
 anonymous
one of each
 amistre64
the last number sign tells us we need to multiply some signs to get it....
 amistre64
good, and the middle tells us which is begger right?
 amistre64
or bigger depending on your accent :)
 anonymous
yes
 amistre64
(x B )(x+L ) we good so far? you writin this down?
 anonymous
yes
 amistre64
2x^22x40
what numbers from our pool will give us 2?
 anonymous
10 8
 anonymous
+10 8
 amistre64
good. lets fill them in
(x10 )(x+8 ) now divide out the first number that "2" we used
(x10/2)(x+8/2) now what?
 anonymous
(x5)(x+4)
 amistre64
thats right.... but let me check our work a second....
 amistre64
one little after thought that usually doesnt come up is this..... we could have factored out a "2" to begin with.
 anonymous
as the gcf
 amistre64
yep.... so we actually need to put it back in like this:
2(x5)(x+4) to make everything right again :)
 amistre64
now this will work back into the original :) you tried to trick me didnt you :)
 anonymous
haha ya
 anonymous
thanks..you helped alot
 amistre64
youre welcome.... hope you do good :)
 anonymous
il get on toarrow night and let you know if your here my class is at 8am
 amistre64
8am eh... is that florida time?
 anonymous
nm
 amistre64
ahh.... your 2 or 3 hours behind me then
 anonymous
ya its 11
 amistre64
:) library is closing here at my college.... so have fun :)
 anonymous
ok im off to bed thanks again
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