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anonymous

  • 5 years ago

how do you factor trinomials

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  1. anonymous
    • 5 years ago
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    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

  2. anonymous
    • 5 years ago
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    I know my teacher cant even do it

  3. anonymous
    • 5 years ago
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    haha do you have a specific problem?

  4. anonymous
    • 5 years ago
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    yeah I just dont know how to do exponents on the computer

  5. anonymous
    • 5 years ago
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    you can use the equation button down on the left of just do shift 6 its the ^ which means exponent

  6. anonymous
    • 5 years ago
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    2x squared- 14x - 36 we have to do polynomials in the x squared+ bx +c

  7. anonymous
    • 5 years ago
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    ok so you have \[2x ^{2} - 14x - 36 =0\]

  8. anonymous
    • 5 years ago
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    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

  9. anonymous
    • 5 years ago
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    sorry the @ is suppose to be 2

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

  11. anonymous
    • 5 years ago
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    yeah good

  12. anonymous
    • 5 years ago
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    oops its \[2 (x ^{2} - 7x - 18) = 0\]

  13. anonymous
    • 5 years ago
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    yeah thats what I got but then I have to find the factors of 18 and then im lost

  14. anonymous
    • 5 years ago
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    yeah ok. so the trick is to find two numbers that add up to -7 but when multiplied together equal -18

  15. anonymous
    • 5 years ago
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    so it would be 2 and 9

  16. anonymous
    • 5 years ago
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    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

  17. anonymous
    • 5 years ago
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    yeah good job

  18. anonymous
    • 5 years ago
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    but then what do you do?

  19. anonymous
    • 5 years ago
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    something like ( x-9) ( x+2)

  20. anonymous
    • 5 years ago
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    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

  21. anonymous
    • 5 years ago
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    oops YES

  22. anonymous
    • 5 years ago
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    haha sorry i mean that

  23. anonymous
    • 5 years ago
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    you are correct

  24. anonymous
    • 5 years ago
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    then you have your roots, x=2, x=-9

  25. anonymous
    • 5 years ago
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    does it matter which one goes where can I switch them and get the samething

  26. anonymous
    • 5 years ago
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    so whats the answer

  27. anonymous
    • 5 years ago
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    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

  28. anonymous
    • 5 years ago
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    those are your roots

  29. anonymous
    • 5 years ago
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    in the back of the book its 2(x+2) (x-9)

  30. anonymous
    • 5 years ago
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    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

  31. anonymous
    • 5 years ago
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    I was solving two but I got as far as the last part. Do you mind helping me on another?

  32. anonymous
    • 5 years ago
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    sure

  33. anonymous
    • 5 years ago
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    -x^3+6x^2+16x I have to solve and factor

  34. anonymous
    • 5 years ago
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    I got x(-x^2+6x+16) is that right?

  35. anonymous
    • 5 years ago
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    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)

  36. anonymous
    • 5 years ago
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    so are the factors then -2 and 8

  37. anonymous
    • 5 years ago
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    are you sure? 8 + -2 = 6

  38. anonymous
    • 5 years ago
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    yeah isnt it?

  39. anonymous
    • 5 years ago
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    no switch the signs. then you have -8 and 2 which -8*2 = -16 and -8 + 2 = -6 which is what we want

  40. anonymous
    • 5 years ago
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    oh we need -6

  41. anonymous
    • 5 years ago
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    so how do you pull a number or variable from 4y-45+y^2

  42. anonymous
    • 5 years ago
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    ok you can't since you have to see that there is no coefficient on y^2

  43. anonymous
    • 5 years ago
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    thats what I thought but in the back of the book it says (y-5) (y+9)

  44. anonymous
    • 5 years ago
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    think of some basic multiples of 45 ...one to try is 5 since 45 ends in 5

  45. anonymous
    • 5 years ago
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    rearrange the polynomial...its really y^2 + 4y - 45

  46. anonymous
    • 5 years ago
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    so all you have to do is factor in a problem like that

  47. anonymous
    • 5 years ago
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    yeah thats it

  48. anonymous
    • 5 years ago
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    so are you doing the same thing with x^2-72+6x

  49. anonymous
    • 5 years ago
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    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.

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