## anonymous one year ago Medal for Matrix help. How would I solve for x? [-8 -14 -2x] = [2 -74 -6]

1. UsukiDoll

what row by column matrix is this?

2. anonymous

1 x 3 for both

3. UsukiDoll

so is A - [-8 -14 2x] and B =[2 -74 -6]?

4. UsukiDoll

it's like find an x that will make both matrices equal...

5. anonymous

Yeah, that's the issue. I have no idea how to find x in this situation. It's been a while since I've done a problem like this.

6. UsukiDoll

oh how about if we have something like this -2x=-6 then we just solve for x. Because what I am assuming is that the last entry in A and B are supposed to be equal.

7. UsukiDoll

I have done these, but with 2x2 or above

8. anonymous

I could give you the possible answers if that would help?

9. anonymous

a. x = -5.7 b. x = -17.7 c. x = 7 d. x = 6

10. UsukiDoll

11. UsukiDoll

what the O_O!

12. anonymous

Yeah...my reaction exactly.

13. UsukiDoll

this is so weird.. I'm calling wolfram lol

14. anonymous

lol okay. That's a good idea. This was the original problem... $[-8 -14-2x] - ([-19 +17 -1] + [14 +13 -2]) = [-3 -44 -9]$

15. UsukiDoll

T_T wait a sec.. I might have ... did you do the operation in paraenthesis first?

16. anonymous

Oops! Ignore the plus signs. I dunno why I put them inside the matrices. and yes I did. Was I not supposed to?

17. UsukiDoll

-.- ok hold on I think I might have see what is going.. yes you should do the ones in paraenthesis first ..

18. Loser66

Question: how A = B??

19. UsukiDoll

that's what I was thinking too.

20. UsukiDoll

what makes A=B ? but when I was to do the problem.. if I let x = 3 that last part will be equal but the first 2 entries aren't equal

21. Loser66

if A = B ,then -8 =2?? -14 =-74 -2x = -6 but how??

22. UsukiDoll

something is wrong with the arithmetic.

23. UsukiDoll

let's do it over... and no shortcut cheats.. now this is the original problem right? $[-8 -14-2x] - ([-19 +17 -1] + [14 +13 -2]) = [-3 -44 -9]$

24. anonymous

That wouldn't surprise me. I've been doing math since about 10 am. and yes it is.

25. UsukiDoll

$[-8, -14,-2x] - ([-19 , 17 , -1] + [14, 13 ,-2]) = [-3, -44, -9]$

26. UsukiDoll

let me put on my cglasses

27. UsukiDoll

now let's do the ones in the () with adding the matrices.

28. UsukiDoll

$- ([-19 , 17 , -1] + [14, 13 ,-2])$

29. UsukiDoll

$- ([-19+14 , 17+13 , -1-2] )$$-[-5,30,-3] \rightarrow [5,-30,3]$

30. UsukiDoll

$[-8 -14-2x] - [5, -30, 3] \rightarrow [-8-5-14-(-30),-2x-3]$ are you sure it's not [8, -14, 2x] ?

31. UsukiDoll

$[8 -14-2x] - [5, -30, 3] \rightarrow [8-5-14-(-30),-2x-3] \rightarrow [3, 14+30,-2x-3] \rightarrow [3, 44, -2x-3$ $\rightarrow [3, 14+30,-2x-3] \rightarrow [3, 44, -2x-3]$

32. UsukiDoll

yay I think I got what x is !

33. UsukiDoll

on the last entry we have to solve for x so now we have $[3, 44, -2x-3] = [3, 44, 9]$

34. anonymous

Really? (sorry, I'm doing this an something else at the same time)

35. UsukiDoll

wait a sec... I think there are typos

36. UsukiDoll

I think.. let me do this on paper.. there is a typo somewhere on your end or something.

37. anonymous

Okay.

38. UsukiDoll

-_- I got x = 3. who are these people giving these choices anyway?

39. UsukiDoll

$[-8, -14, 2x] +[ 5 -30 ,3] = [-8+5, -14-30, 2x+3] = [-3, -44, 2x+3]$

40. anonymous

It's just random questions I'm given for practice. At the moment, I am unable to view the question, but as soon as I can, I'll let you know if there were any typos in my copy.

41. UsukiDoll

$[-3, -44, 2x+3] = [-3, -44, -9]$ there could be typos on my end but I got it... ok THIS TIME I AM CERTAIN I GOT IT!

42. UsukiDoll

we just have to focus on the last equation because our first two entries are equal so we now solve for x for that last entry 2x+3=-9 2x =-9-3 2x=-12 x =- 6 there's a typo in your multiple choice

43. UsukiDoll

yup x = -6 $[-3, -44, 2(-6)+3] = [-3, -44, -12+3] = [-3, -44, -9]$

44. UsukiDoll

yay finally it's over. can I get a medal for this 1 x 3 horror festival? I'm not use to adding and solving like that XD

45. UsukiDoll

-2x+3 = -9 doh I dropped a sign. It's D -2x = -9-3 -2x=-12 x=6

46. anonymous

You're awesome! :D Hopefully I'll never get another question like this again, but thank you so much for all your help.

47. UsukiDoll

that question sucked... I was never given like this and I'm used to adding vertically!

48. anonymous

Honestly, I've never had one like this either. The moment I looked at it, my brain went blank.

49. UsukiDoll

it was tedious. doable but tedious... I think the latex threw me off too. That's why I got so many answers and what not.

50. UsukiDoll

Cleaned up version $[-8 -14-2x] - ([-19 +17 -1] + [14 +13 -2]) = [-3 -44 -9]$ $\[[-8 -14-2x] - ([-19+14 , 17+13 , -1-2] ) = [-3 -44 -9]$ $\[[-8 -14-2x] - ([-5, 30 , -3] ) = [-3 -44 -9]$ $\[[-8 -14-2x] +([5, -30 , 3] ) = [-3 -44 -9]$ $\[[-8+5, -14-30,-2x+3] ) = [-3 -44 -9]$ $\[[-3, -44,-2x+3] ) = [-3 -44 -9]$ $-2x+3=-9$ $-2x+3-3=-9-3$ $-2x=-12$ $\frac{-2x}{-2}=\frac{-12}{-2}$ $x=6$ $\[[-3, -44,-2(6)+3] ) = [-3 -44 -9]$ $\[[-3, -44,-12+3] ) = [-3 -44 -9]$ $\[[-3, -44,-9] ) = [-3 -44 -9]$