Question

how do you factor trinomials

Answer 1

you can use pascal's triangle or the binomial theorem or by factoring the first two and the second two and seeing if a common factor emerges...its kind of hard to explain

Answer 2

I know my teacher cant even do it

Answer 3

haha do you have a specific problem?

Answer 4

yeah I just dont know how to do exponents on the computer

Answer 5

you can use the equation button down on the left of just do shift 6 its the ^ which means exponent

Answer 6

2x squared- 14x - 36
we have to do polynomials in the x squared+ bx +c

Answer 7

ok so you have \[2x ^{2} - 14x - 36 =0\]

Answer 8

no we have to pull the lowest number and the lowest variable then divide each term by that so I know its @ because they all dont have a common variable then divide each term by 2

Answer 9

sorry the @ is suppose to be 2

Answer 10

ok so notice all the coefficients can be factored out a 2 so you have\[ (x ^{2} - 7x - 16) = 0\]

Answer 11

yeah good

Answer 12

oops its \[2 (x ^{2} - 7x - 18) = 0\]

Answer 13

yeah thats what I got but then I have to find the factors of 18 and then im lost

Answer 14

yeah ok. so the trick is to find two numbers that add up to -7 but when multiplied together equal -18

Answer 15

so it would be 2 and 9

Answer 16

so look at 9 and 2. 9*2 = 18 but you want one to be negative so you have -18 and you want them to add to -7. so try -9*2 = -18 and -9 + 2 = -7

Answer 17

yeah good job

Answer 18

but then what do you do?

Answer 19

something like ( x-9) ( x+2)

Answer 20

ok so now you factor them you know one is -9 and one is 2 so you subtract them from x. you get
(x-2)(x+9)=0 and by FOILing you get x^2 -7x -18 = 0

Answer 21

oops
YES

Answer 22

haha sorry i mean that

Answer 23

you are correct

Answer 24

then you have your roots, x=2, x=-9

Answer 25

does it matter which one goes where can I switch them and get the samething

Answer 26

so whats the answer

Answer 27

no it does matter
if you had what i put you'd have (x-2)(x+9) = 0 and you get x^2 + 7x - 18 which is not correct.

the answer is x =-2, x = 9

Answer 28

those are your roots

Answer 29

in the back of the book its 2(x+2) (x-9)

Answer 30

oh you were just factoring? sorry i thought you were solving.
yeah we factored out the 2 remember? we have to bring it back in
so mulitply it by what you told me
and its the answer

Answer 31

I was solving two but I got as far as the last part. Do you mind helping me on another?

Answer 32

sure

Answer 33

-x^3+6x^2+16x I have to solve and factor

Answer 34

I got x(-x^2+6x+16) is that right?

Answer 35

yeah you could do that but it might be easier to factor out a negative. just so its a little simpler to look at. so you could just have -x(x^2 -6x - 16)

Answer 36

so are the factors then -2 and 8

Answer 37

are you sure? 8 + -2 = 6

Answer 38

yeah isnt it?

Answer 39

no switch the signs. then you have -8 and 2 which -8*2 = -16 and -8 + 2 = -6 which is what we want

Answer 40

oh we need -6

Answer 41

so how do you pull a number or variable from 4y-45+y^2

Answer 42

ok you can't since you have to see that there is no coefficient on y^2

Answer 43

thats what I thought but in the back of the book it says (y-5) (y+9)

Answer 44

think of some basic multiples of 45 ...one to try is 5 since 45 ends in 5

Answer 45

rearrange the polynomial...its really y^2 + 4y - 45

Answer 46

so all you have to do is factor in a problem like that

Answer 47

yeah thats it

Answer 48

so are you doing the same thing with x^2-72+6x

Answer 49

yeah exactly the same. sometimes if it helps you to see it you should rewrite it in the form ax^2 + bx + c to see it. if you can already see it then it doesnt matter.