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Homework Statement
Homework Equations
none
The Attempt at a Solution
Is this correct?
Thanks.
The answer is correct.Evangeline101 said:Homework Statement
[ ATTACH=full]101053[/ATTACH]
Homework Equations
none
The Attempt at a Solution
[ ATTACH=full]101054[/ATTACH]
Is this correct?
Thanks.
Evangeline101 said:Homework Statement
View attachment 101053
Homework Equations
none
The Attempt at a Solution
View attachment 101054
Is this correct?
Thanks.
SammyS said:The answer is correct.
There are errors in your work starting with the table.
If x is the speed from Tokyo to Bangkok then reducing that by 200 gives a speed of x - 200 from Bangkok to Tokyo. Etc.
There's still a problem, x is the Tokyo to Bangkok speed. That can't be 600mph. 600 - 200 is 400, and that doesn't work out.Evangeline101 said:I understand where I made the error, the return trip speed decreased by 200 km/h, so it should have been (x-200) not (x+200), so I have corrected my answer:
[ ATTACH=full]101104[/ATTACH]
Thanks for the help! :)
SammyS said:There's still a problem, x is the Tokyo to Bangkok speed. That can't be 600mph. 600 - 200 is 400, and that doesn't work out.
So, where is the problem?
You made a couple of errors.
Sign errors in going from
−960000=2x2−400x−960000=2x2−400x-960000=2x^2-400x to
2x2+400x−960000=02x2+400x−960000=02x^2+400x-960000= 0 It should be
2x2−400x+960000=02x2−400x+960000=02x^2-400x+960000= 0 But there is no real solution to that.
SammyS said:The problem is that it's the Tokyo to Bangkok time that's smaller, because the speed is greater. When you subtract to get 2 hours, you need to subtract in the opposite order.
If x > 200, thenEvangeline101 said:I tried doing it this way, but as you said there is no real solution.
I don't understand what you mean, can you please explain?
SammyS said:If x > 200, then
4800x−200>4800x4800x−200>4800x\displaystyle \frac{4800}{x-200}>\frac{4800}{x}.
So you had these reversed.
It's what is needed of you want to make everything consistent.Evangeline101 said:So even if I switch these two, can I not get the same answer I had originally? How does switching the two help with the answer to the problem? or is it just the proper way to write it?
SammyS said:It's what is needed of you want to make everything consistent.
As I stated in my first reply, the answer you gave for the time from Bangkok to Tokyo was correct. (600 km/hr)
But you had a number of inconsistencies.
Added in Edit:
You should get x = 800. Then x- 200 = 600, the answer.
No.Not like that.Evangeline101 said:
SammyS said:You should get x = 800. Then x- 200 = 600, the answer.
Right. And they did not make algebra mistakes. You did.Evangeline101 said:This is an example from my lesson that I have been using as a reference to solve my problem:
View attachment 101173
View attachment 101174
SammyS said:No.Not like that.
The first three lines are correct.
After that, there are at least two Algebra mistakes.
Yes. That looks to be correct.Evangeline101 said:View attachment 101177
4800x - 4800x + 960 000 = 2x2 - 400x (960 000 is positive because I multiplied -4800 and -200)
960 000 = 2x2 - 400x (Now I move 960 000 to the right side and it becomes -960 000)
2x2 - 400x - 960 000 = 0
x2 - 200x - 480 000 = 0
(x+600) (x-800) = 0
x= -600 or x = 800
Does this make more sense? did I fix the algebra errors? if not please show me where I made errors.
SammyS said:You should get x = 800. Then x- 200 = 600, the answer.