In the equation 1/j +1/k = 1/3, both j & k are positive integers. What is the sum of all possible values for k?
WHAT I HAVE SO FAR:
J+K 1
___ = _____
JK 3
Right?
What can I do from here?
I have not worked out how to do it formally and I won't guarentee that what i think is correct.
I don't think what you have done is helpful because the answers for j and k must be integers
I have only found 1 solution set for j and k, well 2 really because k and j are interchangable.
Can you find one answer, just by mucking around with the numbers?
Not sure if it helps but,
Solving for k
k= 3j/j-3 , Notice J can't be equal to 3
If J and K are positive integers,
Is there a restricted domain?
Also J can't be equal to=(1,2,3,5,7,8,9,10,11,13,14,15,16,17,18,19,20,21,22, etc..) The pattern contuines so, k can be equal to 4, 6 ,12only out of the first 20 numbers.. I don't think the equation works for more... Idk.
so the sum of possible values of k is 4+6+12=22
P.S for these type of questions, the best strategy is just trying numbers and see if you notice a pattern as this question doesn't have a specific pattern but only 3 out of the first 30 numbers worked, Then they only can work i guess.(There is usually a restricted domain for these questions like x
https://www.desmos.com/calculator
Type your question here but let k=x and j=y or vice versa and notice that k=j at 6
also when k or j = 4 the other = 12
Also notice that it will approach 3 but can't equal to 3 as it will be undefined.
Here is my attempt:
Good job on finding \( 0=-3j+jk-3k\) guys, we can work from here?
We factor:
\(0=j(-3+k)-3k\)
Simplifies to:
\(0=j(k-3)-3k\)
We add 9 to both sides, this allows us to factor better:
\(9=j(k-3)-3k+9\)
We factor once again
\(9=j(k-3)-3(k-3)\)
We then simplify:
\(9=(j-3)(k-3)\)
Now that we have a binomial expression, we can list the factors of 9 to guess solutions.
1 and 9
3 and 3.
So for 1 and 9, we set them equal
\(j-3=1\)
\(k-3=9\)
Solving this, we get J=4 and k=12, since they can be reversed, the values of K and be 4 or 12.
Now we solve 3 and 3
\(j-3=3\)
\(k-3=3\)
Solving this, we get J=6 and K=6, since they can be reversed, the values of K can only be 6.
So the possible values for K can be 4, 6, and 12.
The sum of that is \(\boxed{22}\)
A factor of 9 is also -3 and -3. But do you know why it doesn't work?
both j & k are positive integers
The question says that j and k have to be positive.
This is why it doesn't work, becuase when you add three to both sides, j and k become 0.
0 is neither positive or negative. So 0 is not a solution