conic problem

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Sonal7

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Screenshot 2020-09-09 at 12.06.01.png

Screenshot 2020-09-09 at 12.41.18.png

I am not sure how they got the value for X. It doesn fit with putting in the value of y in xy=c^2.
 

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Subhotosh Khan said:
They used the equation described in 4th line above. Please be careful about distinction of 'x' and 'X'.
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sorry I cant understand what 4th line means? I cant see what you are implying. I tried all the equations and none of them worked.
 
Sonal7 said:
sorry I cant understand what 4th line means? I cant see what you are implying. I tried all the equations and none of them worked.
Click to expand...
You have two attachments! Look at the 2nd attachment - where they solve problem 5a and give you the equation for the tangent.
 
no
Subhotosh Khan said:
You have two attachments! Look at the 2nd attachment - where they solve problem 5a and give you the equation for the tangent.
Click to expand...
I think thats wrong, they wont expect you to do part (a) by using part (b)- you have to move in the order or a first. You cant use the equation from the later part. Its a bit of cheating :)
 
Sonal7 said:
no

I think thats wrong, they wont expect you to do part (a) by using part (b)- you have to move in the order or a first. You cant use the equation from the later part. Its a bit of cheating :)
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Who mentioned part (b) at all? SK was referring to the 4th line in their solution of (a), above the point you are asking about: x + q^2y = 2cq. Just replace y with the value they just got for it, 2c/(p+q).
 
Dr.Peterson said:
Who mentioned part (b) at all? SK was referring to the 4th line in their solution of (a), above the point you are asking about: x + q^2y = 2cq. Just replace y with the value they just got for it, 2c/(p+q).
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It seems to work when you come along. SK was absolutely correct. Its worked. I get scared with complex alegbra but its worked out again.

I have made a mistake, i missed out a q in the answer. Its been dropped accidently.
20200909_211046.jpg
 
Last edited by a moderator:
On your last two lines, replace p in the numerator with pq. Did you not notice that your result was different from theirs?

In one algebra course I have taught, I emphasize one idea from start to finish: Every line you write, check it against the line before! This is the only way to avoid the silly errors we all make. And when you know you can do that, the algebra becomes less scary!
 
Dr.Peterson said:
On your last two lines, replace p in the numerator with pq. Did you not notice that your result was different from theirs?

In one algebra course I have taught, I emphasize one idea from start to finish: Every line you write, check it against the line before! This is the only way to avoid the silly errors we all make. And when you know you can do that, the algebra becomes less scary!
Click to expand...
Yes I know, I corrected this. I redid this. I mentioned that above the picture of the working. I accidentally dropped the q.
 
Ah! With such a large picture, I didn't see what you wrote above it while replying.
 
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