Math help (1 Viewer)

[D94]

Wait. How does that work then? Because for this question:



and this is what I have so far:









???

What do I do next? because there are two unknowns?

You've done the sum of the roots, now work out the product of the roots = c'/a' = 2 = a(a+1).

So solve a(a+1) = 2 to find the value of a, and substitute this into the equation with a and m.

 

[Fawun]

1. Use alpha, don't interchange alphe with "a".

2. Use the product of the roots since you only get one variable.

Okay so how would I know which one will give me one variable without having to do it and finding out that it gives me two variables if that makes sense?

 

[SpiralFlex]

Okay so how would I know which one will give me one variable without having to do it and finding out that it gives me two variables if that makes sense?

If you used the sum of the roots just then, you got two variables alpha and "m". So whatever alpha is will be dependent on the value of m. However, for any value of m, the product of the roots will ALWAYS be 2.

 

[Fawun]

You've done the sum of the roots, now work out the product of the roots = c'/a' = 2 = a(a+1).

So solve a(a+1) = 2 to find the value of a, and substitute this into the equation with a and m.

If I was given another similar question, do I have to do the sum of the roots? do I have to do both or can I just do one of it?

 

[SpiralFlex]

The final step of my working would be substituting the alpha into the original equation to find m.

 

[SpiralFlex]

If I was given another similar question, do I have to do the sum of the roots? do I have to do both or can I just do one of it?

Depends on the question, but you will see which one gives you a definite value and which will led you no where.

 

[Fawun]

You've done the sum of the roots, now work out the product of the roots = c'/a' = 2 = a(a+1).

So solve a(a+1) = 2 to find the value of a, and substitute this into the equation with a and m.

Why do you have to substitute it back into the equation?

 

[SpiralFlex]

Why do you have to substitute it back into the equation?

You found alpha but not m. Which is in the question.

 

[Fawun]

You found alpha but not m. Which is in the question.

Why would you sub it though? because before, you said that k=-1 which is what the answer is according to the answers?

 

[SpiralFlex]

Why would you sub it though? because before, you said that k=-1 which is what the answer is according to the answers?

Yes. There's a reason we found alpha.

If you find a definite value for alpha, then we can substitute it into the original question and you get say for example

 

[Fawun]

Yes. There's a reason we found alpha.

If you find a definite value for alpha, then we can substitute it into the original question and you get say for example

So then why does the answers in the back say that alpha was correct?

So for the above question, by doing the products of the roots:









sub them back into the original equation:

For a=-2





For a=1





but the answer says that

?

 

[SpiralFlex]

So then why does the answers in the back say that alpha was correct?

So for the above question, by doing the products of the roots:









sub them back into the original equation:

For a=-2





For a=1





but the answer says that

?

Correct, I showed you what alpha + 1 was (other root) so you understand the concept of consecutive roots.

 

[SpiralFlex]

Check your first "m" value. You made a silly mistake.

 

[Fawun]

Correct, I showed you what alpha + 1 was (other root) so you understand the concept of consecutive roots.

What the

You didn't answer my question lol

How come the answer is m=plusminus 3?

From substitution, I had m=4 and m=-3

 

[Fawun]

Check your first "m" value. You made a silly mistake.

Oh wow lol my bad. Thanks Spiral

 

[SpiralFlex]

Young Fawn you are developing well.

 

[HSC2014]

inb4 Fawun is best here at maths in 2014

 

[D94]

If I was given another similar question, do I have to do the sum of the roots? do I have to do both or can I just do one of it?

In any situation, not only in this sum/product of roots questions, if you have 2 unknowns, you need 2 equations with those 2 unknowns in them to solve the question or at least one equation which solves one of the unknown variables.

The question asking to find k, since you have one equation which solves for k, you only need that equation. Why would you bother with another when you've already answered the question? Now, in the previous equation, you have one equation with a and m as unknown variables. You must have another equation with either 1 or 2 of the variables in order to solve for either of the unknowns. So after you found what 'a' was, you now have 2 equations which can be used to find the value of m.

You need to know what you're trying to solve and look for relevant equations which help you solve for those unknowns.

 

[deswa1]

inb4 Fawun is best here at maths in 2014

Yeah let's not get ahead of ourselves

Nah but seriously- see Fawun- you're improving rapidly. I'm serious, by year 12 you could legit be heaps good at maths. I believe in you

 

[RealiseNothing]

If fawun did what I did in the coming January holidays, she legit could be very good.