## jay3390 3 years ago Subtract. [(u)/(6c^3*d)] - [(3c^3*w^3)/(8b^2*d^2)] Simplify your answer as much as possible

1. jay3390

Help is greatly appreciated

2. saifoo.khan

Find LCD.

3. jay3390

dont know how to do this :/

4. saifoo.khan

@Tomas.A . help.

5. jay3390

that would be great if you could help!

6. saifoo.khan

Ok.

7. Tomas.A

$[(u)/(6c^3*d)] - [(3c^3*w^3)/(8b^2*d^2)]$

8. saifoo.khan

|dw:1339902311825:dw|it's like that right?

9. jay3390

yeah

10. saifoo.khan

So what do u think of LCD?

11. jay3390

im not really sure, i suck at fractions :/

12. saifoo.khan

dont worry about fractions. it's easy. you have two things: 6c^3*d and 8b^2*d^2 open up, the numbers: 6,8 variables: c^3, d variables: b^2 d^2 agree?

13. jay3390

Right

14. saifoo.khan

So the LCD will be, 6*8 = 48 for variables, c^3 and b^2. now what about d and d^2 we always take the bigger term, so we will take d^2. Therefore our LCD will be, 48*c^3*b^2*d^2

15. jay3390

oh okay perfect, then what??

16. saifoo.khan

now, |dw:1339902810873:dw|Do you get this step?

17. jay3390

for the most part, yeah

18. saifoo.khan

What we have to do is, we have to make the denominators same as LCD. so we had 6c^3d.. and we have to make it as 48c^3b^2d^2 we have to multiply 6c^3d with something to make it as 48c^3b^2d^2 so we multiplied by 8b^2d.

19. jay3390

oh okay and for the numerator??

20. saifoo.khan

When we multiply that for denominator, we multiply the same thing with numerator.

21. jay3390

how do i multiply that out though? :/

22. saifoo.khan

$\Large \frac{48c^3b^2d^2}{6c^3d} \to8b^2d.$

23. jay3390

woah..thats the numerator?

24. saifoo.khan

Yes sir.

25. saifoo.khan

that's what u have to multiply with numerator.

26. jay3390

i must be driving you crazy, lol, but i dont get how to multiply it and simplify afterwards.. :/

27. saifoo.khan

C'mon. chill up!

28. saifoo.khan

and tell me where are u stuck.

29. jay3390

i got the denominator, now i need to get the numerator and then simplify. i know what to multiply but i dont know how :/ i get some super long answer with a bunch of variables

30. saifoo.khan

whatever you multiply with denominator.. you have to multiply the same thing with the numerator.

31. jay3390

yeah

32. saifoo.khan

So now, u(8b^2d) = 8b^2du

33. jay3390

so, 8b^2du - 3c^3w^3?

34. saifoo.khan

you forgot to multiply the right denominator and then the numerator.

35. saifoo.khan

you did it with left one right? now do it with right one as well.

36. jay3390

so it would be 6c^3*d(3c^3*w^3)?

37. saifoo.khan

No. since the denominators are different. we will do something like:|dw:1339903883124:dw|

38. jay3390

ohh okay and once i get that, the top would be 8b^2du-18c^6w^3?

39. saifoo.khan

Yes sir. that answer over $\Large \frac{8b^2du-18c^6w^3}{48c^3 b^2 d^2}$

40. jay3390

okay and does that get simplified further??

41. saifoo.khan

Yes. you can take commons.

42. jay3390

like the b^2?

43. saifoo.khan

b^2 is not in the second term.

44. jay3390

ahh :( idk how then

45. saifoo.khan

HINT: 8 and 18

46. jay3390

-10b^2*d*u*c^6*w^3/48c^3*b^2*d^2??

47. saifoo.khan

umm... no

48. jay3390

:/

49. saifoo.khan

|dw:1339904363228:dw|

50. jay3390

then theres more left to simplify or no?

51. saifoo.khan
52. jay3390

lol okay, thank you SOOOO much!!

53. saifoo.khan

No problem! (:

54. jay3390

:) thanks again!

55. saifoo.khan

Welcome.