Algebra question.

dublinstudent.

Can somebody please explain this one to me.

I need to isolate Z. I have been given the solution as it is a practice test but I don't get the second line (marked with a star). Also, the final result as given does not tally with any of the multiple choice answers supplied.


1. What is happening where starred? I would have multiplied both sides by x+root whatever, but supplied solution doesnt.
2. Given final line is solution supplied, why does it not match any of the given answers.
Thank you.

The Continental Op

Caveat - I've not done any algerbra in 45 years.

Without looking at the working out or answers I did it myself and got to the answer in the solution given so that seems to be right but I can't for the life of me find any one of the answers that fits?

Where you star is I got to that stage by multiplying both sides by (x+√Z) and then dividing both by (r-2)

dublinstudent.

The Continental Op wrote: »

Caveat - I've not done any algerbra in 45 years.

Without looking at the working out or answers I did it myself and got to the answer in the solution given so that seems to be right but I can't for the life of me find an one of the answers that fits?

So what is happening on the second line with the star? To remove the 1/xxxx on the right , multiply both sides by xxxx, but he didnt, and it now has 1/whatever on the left........

The Continental Op

dublinstudent. wrote: »

So what is happening on the second line with the star? To remove the 1/xxxx on the right , multiply both sides by xxxx, but he didnt, and it now has 1/whatever on the left........

See above

Quackster

The answer bottom left is exactly the same as A, just written differently.

jogdish

Looks like A), the solution while correct has not been expressed as a single fraction. Make a common fraction of the r-2 on the bottom and it should be (doing it in my head) it.

The Continental Op

Quackster wrote: »

The answer bottom left is exactly the same as A, just written differently.

Don't see that but be delighted if you can explain how the worked answer is the same? The old brain needs a workout occasionally.

Quackster

dublinstudent. wrote: »

So what is happening on the second line with the star? To remove the 1/xxxx on the right , multiply both sides by xxxx, but he didnt, and it now has 1/whatever on the left........

The equation has been inverted. If X = 1/Y, then 1/X = Y. You can just flip the equation over.

Quackster

The Continental Op wrote: »

Don't see that but be delighted if you can explain how the worked answer is the same? The old brain needs a workout occasionally.

As previous poster says, 1/(R-2) - X = (1 - RX + 2X)/(R-2) as you multiply -X by R-2 to create a single fraction.

ozmo

They flipped both sides - you can do that.
so
1/2 = 1/x
becomes
2/1 = x/1 (and x = 2

in your case (r-2)/1 becomes 1/(r-2) and the other side becomes something/1

The Continental Op

Quackster wrote: »

As previous poster says, 1/(R-2) - X = (1 - RX + 2X)/(R-2) as you multiply -X by R-2 to create a single fraction.

OK got there in the end

Pythagorean

Tricky enough !! I found ABCD hard going, as regards the starred line, a numerical example may help;
3= 1/1/3 therefore

1/1/3=3/1 ( or if 1/a =b then 1/b =a)

Hope this helps !!

mirrorwall14

Walk through P1 explaining the star

mirrorwall14

Walkthrough P2


Current post primary maths teacher.

You can do the same thing to both sides of an equation always (we used to just learn the outcome of doing that step, we now show it)

You need to be able to find a common denominator to make the answer ‘look’ correct

dublinstudent.

So, some interesting ideas there. Will print it all out and try to follow and understand your explanations.
It is great you all answered at such a late hour. Thank you.

mirrorwall14

dublinstudent. wrote: »

So, some interesting ideas there. Will print it all out and try to follow and understand your explanations.
It is great you all answered at such a late hour. Thank you.

Hope you got sorted. I can do a quick walkthrough video at some stage for it if you need it.

dublinstudent.

mirrorwall14 wrote: »

Hope you got sorted. I can do a quick walkthrough video at some stage for it if you need it.

I need to sit down with a clear head and review this. Thank you for the offer.