# I need formulaes

1. Feb 23, 2010

### storoi1990

1. The problem statement, all variables and given/known data

Does anybody know of some good mathematics formula books?

i am currently stuck with: X/5

Can i turn this into something else, like: X-5?

i got this from the equation: X+ 5y = 3000

then: 5y = 3000 - x

y = 600 - x/5

Now i have to put this into a Lagranges equation:

f(x,y) = 100x^1/2 + 100y^1/2-1000

wich i now get: 100x^1/2 + 100 (600-x/5)^1/2-1000

how do i solve this?

2. Relevant equations

3. The attempt at a solution

Last edited: Feb 23, 2010
2. Feb 23, 2010

### HallsofIvy

What, exactly are you trying to do? You talk about "solving" an equation, but you have no equation. IF what you have is set equal to something, typically, what you would need to do is isolate the square roots on opposite sides of the equals sign and square both sides. You probably will need to square twice.

3. Feb 23, 2010

### Staff: Mentor

What you're asking for doesn't exist.
About the only thing you can do with x/5 is to write it as a product: x * (1/5). About the only thing you can do with x - 5 is to write it as a sum: x + (-5). You can always write a quotient of two expressions as a product of one of them times the reciprocal of the other, and you can always write a sum of two expressions as one of them plus the additive inverse of the other, but that's about it.