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youngnephew34

  • one year ago

What is the value of y in rhombus LMNO A)4 B)6 C)12 D)24

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  1. youngnephew34
    • one year ago
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  2. phi
    • one year ago
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    try to write an equation that shows the two halves of a diagonal are equal

  3. youngnephew34
    • one year ago
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    |dw:1440159145510:dw|

  4. youngnephew34
    • one year ago
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    hold on

  5. youngnephew34
    • one year ago
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    Y+12=6x

  6. phi
    • one year ago
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    yes, now write the other equation (for the other diagonal)

  7. youngnephew34
    • one year ago
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    \[Y=3x\]

  8. phi
    • one year ago
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    we have two equations and two unknowns (x and y are the unknowns) do you know how to solve them? Y+12=6x y= 3x

  9. phi
    • one year ago
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    one way is to use "substitution", the other way is "elimination"

  10. youngnephew34
    • one year ago
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    For the Y+12=6x don't you suppose to subtract one side from another

  11. phi
    • one year ago
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    in this problem, substitution works pretty well. start with the equations: y+12=6x y= 3x notice the 2nd equation says "y is the *same thing* as 3x" we use that to replace the y in the first equation with 3x (erase the y and put in 3x instead) can you do that?

  12. youngnephew34
    • one year ago
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    you will substitute the 3x in to y right

  13. phi
    • one year ago
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    what equation do you get ?

  14. phi
    • one year ago
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    erase the y and put in 3x instead

  15. youngnephew34
    • one year ago
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    so 3x+12=6x

  16. phi
    • one year ago
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    yes. now we have just 1 unknown... that is good. to solve I would start by adding -3x to both sides, like this 3x - 3x + 12 = 6x - 3x now simplify

  17. phi
    • one year ago
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    on the right side you have 6 x's take away 3 x's. how many x's do we have?

  18. youngnephew34
    • one year ago
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    3x

  19. phi
    • one year ago
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    ok, but write out the whole equation (so we don't get confused) 3x - 3x + 12 = 3x on the right side, we have 3x's take away 3 x's

  20. phi
    • one year ago
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    *left side

  21. youngnephew34
    • one year ago
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    3x+12=3x

  22. phi
    • one year ago
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    almost. 3x - 3x is not 3x

  23. youngnephew34
    • one year ago
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    so really 12=3x

  24. phi
    • one year ago
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    yes last step. divide both sides by 3

  25. youngnephew34
    • one year ago
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    x=4

  26. phi
    • one year ago
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    the question asks for "y" not x but from the equations we know y= 3x can you find y (knowing x is 4) ?

  27. youngnephew34
    • one year ago
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    Y=4 srry bout that

  28. phi
    • one year ago
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    no, you were correct the first time x=4 but we can find y using y= 3*x

  29. youngnephew34
    • one year ago
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    so divide 4=3x

  30. phi
    • one year ago
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    y= 3x says y is the same thing as 3 times x if we knew what x is (as a number) we would multiply it by 3 and we would get y (as a number) but from the earlier steps you found x is 4 that means we can find y using that equation. can you try?

  31. phi
    • one year ago
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    in other words, in y= 3*x erase the x and put in 4 instead (because x is the same thing as 4)

  32. youngnephew34
    • one year ago
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    Instead you would do 4x3 right

  33. phi
    • one year ago
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    yes, but write it 4*3 (because using x for multiply is confusing... it might mean "x" the variable)

  34. youngnephew34
    • one year ago
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    ok so 4*3=12

  35. phi
    • one year ago
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    right, y=3x y=3*4 y=12 this problem took lots of steps. See if you can go over the steps, and try to understand the way we found y is 12.

  36. youngnephew34
    • one year ago
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    so 3x+12+6x 3x-6x=3x 12/3=3/3 12/3=4 x=4 4x3=12

  37. phi
    • one year ago
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    3x+12=6x then add -3x to both sides 3x-3x + 12 = 6x-3x simplify to get 0+12 = 3x or 12=3x <-- notice we have 3x, not just 3) 4=x

  38. phi
    • one year ago
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    then use y=3x when x is 4 then y = 3*4 =12

  39. youngnephew34
    • one year ago
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    ok got it and one more to check

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