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neverforgetvivistee

  • 4 years ago

subtracting rational expressions: 7x x-2 --- - ------ 2x 20x+16 please include steps if possible

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  1. moneybird
    • 4 years ago
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    \[\frac{7x}{2x} - \frac{x-2}{20x+16}\] ?

  2. neverforgetvivistee
    • 4 years ago
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    yes

  3. PratikBhandari
    • 4 years ago
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    just take Lcm 2x(20x+16) and solve in as usual way

  4. moneybird
    • 4 years ago
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    \[\frac{7}{2} - \frac{x-2}{4(5x+4)}\]

  5. moneybird
    • 4 years ago
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    multiply 2(5x+4) both top and bottom of fraction 7/2

  6. Mertsj
    • 4 years ago
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    Reduce the first fraction to 7/2. Now the common denominator is 2(10x+8) When you rewrite the first fraction with that denominator, it becomes 7(10x+8)/2(10x+8). since the second fraction already has that denominator, it does not change so now the problem is (70x+56-x+2)/2(10x+8) or (69x+58)/2(10x+8)

  7. neverforgetvivistee
    • 4 years ago
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    why 2(5x+4) and not 4(5x+4)?why 2(5x+4) and not 4(5x+4)?

  8. neverforgetvivistee
    • 4 years ago
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    why 2(5x+4) and not 4(5x+4)?

  9. neverforgetvivistee
    • 4 years ago
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    when i factor 20x+16 I get 4(5x+4)

  10. neverforgetvivistee
    • 4 years ago
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    why do you multiply times 2(5x+4) anmd not 4(5x+4)?

  11. Mertsj
    • 4 years ago
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    Because the first fraction has a denominator of two. So rewrite the denominator of the second fraction as 2(10x+8). Now ask yourself: By what should I multiply the first denominator which is 2 to get the second denominator which is 2(10x+8)? Isn't it clear that the answer is "multiply by (10x+8)"? Then do the same thing to the numerator.

  12. neverforgetvivistee
    • 4 years ago
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    how di you get 2(10x+8)?

  13. neverforgetvivistee
    • 4 years ago
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    did*

  14. Mertsj
    • 4 years ago
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    I took the denominator of the second fraction which is 20x + 16 and factored out a 2 . Since 20x+16 = 2(10x+8) they are equivalent

  15. neverforgetvivistee
    • 4 years ago
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    you're just trying to make it equal to the other denomitaor?

  16. Mertsj
    • 4 years ago
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    The reason I factored out the two is because the denominator of the first fraction is 2 and I wanted to see what I should multiply the first fraction by to get the same denominator the second fraction has.

  17. neverforgetvivistee
    • 4 years ago
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    or it always hast to be the lcm?

  18. neverforgetvivistee
    • 4 years ago
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    or it always hast to be the lcm?

  19. Mertsj
    • 4 years ago
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    Yes, love. You cannot subtract two fractions unless they have the same denominator.

  20. neverforgetvivistee
    • 4 years ago
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    but i mean you divide it to the lcm or just to make it equal to the other fraction?

  21. Mertsj
    • 4 years ago
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    It is most efficient if the denominator is the LCM of both denominators but not mandatory. If the denominators are the same then the fractions can be subtracted.

  22. neverforgetvivistee
    • 4 years ago
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    ok th

  23. neverforgetvivistee
    • 4 years ago
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    thanks

  24. neverforgetvivistee
    • 4 years ago
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    thanks

  25. Mertsj
    • 4 years ago
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    You can see that 20x+16 is the LCM of 2 and 20x+16. I only wrote 20x+16 as 2(10x+8) to make it clear that 20x+16 IS the LCM

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