Differentiate:x^2 + y^2 = 4
You get this:2x + 2yy' = 0
bring the x variable on the other side:2yy' = -2x
Now divide 2y to leave y' by itself:y' = -2x/2y
Answer: y' = -x/y
The given relation is not a implicit solution to the given differential equation.
$14.60 would be your answer
Let m and j be the current ages of Matthew and Jenny, respectively.
Now, Matthew is 3 times as old as Jenny, so the variables are in the following relation:

In 7 years, both of them will be 7 years older, i.e. their ages will be m+7 and j+7, and Matthew will be twice as old:

Now, remembering that m=3j, we can rewrite the second equation as

So, Jenny is 7 and Matthew is 21 (he's 3 times older).
In fact, in 7 years, they will be 14 and 28, and Matthew will be twice as old.
To answer this all you need to do is divide 120 by 50
120/50
2.4
So it will take 2 hours and 24 minutes (.4 of 60 to get the 24)
Divide the total amount of money by the total amount of feet.
477.84/32 = $14.93
hope this helps :)