# Help with finding certain values in non-linear relationships unit. (1 Viewer)

#### AlienWithLiberty610

##### New Member Doing the basics of non-linear relationships, but I’m still stuck on how to solve to find the highlighted parts. Simply rearranging the equation doesn’t give me the right answer. Substituting values for x and y from a graph also don’t give me the value I want. Please help. Is there some formula I’m not aware of or is this a trial and error process? Am I thinking too much? I have a test in a few days, and while I am alright with the topic so far, this really throws me off as I can’t find any appropriate notes on it to help me. Thank you!

#### ExtremelyBoredUser

##### Well-Known Member
I'm not sure why you're not able to get the coefficient value from substituting (X,Y) coordinates. The only thing I can reason why you wouldn't get the coefficient is that:

A) the coordinates aren't on the graph; not produced by the function/relation
B) You're rearranging it wrong

Could you post a sample problem that you're struggling with and show your working out for more clarification

#### AlienWithLiberty610

##### New Member
I'm not sure why you're not able to get the coefficient value from substituting (X,Y) coordinates. The only thing I can reason why you wouldn't get the coefficient is that:

A) the coordinates aren't on the graph; not produced by the function/relation
B) You're rearranging it wrong

Could you post a sample problem that you're struggling with and show your working out for more clarification
I think my problem may be A.
Anyway, here is the question. Answer is in black pen. The task was to find the equation of the graph. This is a cubic, so it is x to the power of 3. Negative four y intercept means that it has been moved down by four.

What I was confused on was why it would be simply x, and not 2x or 3x and so on. What determines a? Another one. This is a hyperbola, meaning something over x. It has been moved down 3 places, hence the minus 3. But why is the k value 2? Why not 1 or 3 or so on?

Does this explain my query?

#### ExtremelyBoredUser

##### Well-Known Member
I have an exam tomorrow so I can't respond today. As soon as my exam finishes I'll give a more elaborate response on why it is. Just to quickly give it, your supposed to find the intercept:

for the 2nd one, use your ruler and try to find a coordinate, so I went for -2. I got the correlating value to be -4. So the coordinates were (-2,-4)

-4 = k/x - 3 (-3 since the hor. asymptote is -3 and y cant equal the b value)
-1 = k/-2
2 = k

I'll explain more later once again but thats the gist of it, the challenge of these questions is you would need to find exact coordinates to find for k to then arrange it. It couldn't be k = 1 as a normal hyperbole graph or else the y value for -2 would be -3.5 which is clearly not whats on the graph etc.

• AlienWithLiberty610

#### AlienWithLiberty610

##### New Member
I have an exam tomorrow so I can't respond today. As soon as my exam finishes I'll give a more elaborate response on why it is. Just to quickly give it, your supposed to find the intercept:

for the 2nd one, use your ruler and try to find a coordinate, so I went for -2. I got the correlating value to be -4. So the coordinates were (-2,-4)

-4 = k/x - 3 (-3 since the hor. asymptote is -3 and y cant equal the b value)
-1 = k/-2
2 = k

I'll explain more later once again but thats the gist of it, the challenge of these questions is you would need to find exact coordinates to find for k to then arrange it. It couldn't be k = 1 as a normal hyperbole graph or else the y value for -2 would be -3.5 which is clearly not whats on the graph etc.
Argh dammit gotta use that ruler. Makes sense, thank you. Finding exact coordinates is pain, but I get your point.

Good luck for your exam! I look forward to seeing the in-depth explanation as it will help me out a lot.