Wait, by saying "Describe the maximum value of OP..." do you mean find the maximum distance between O and the curve P? Also, you have written the two equations separated by a comma. By that I'm assuming you mean that P is the intersection?

By looking at G = ... I think I'm seeing the distance OP squared + the two constraints? I don't know how you do L Multipliers but the way I've learned is this:

You set (if that's the distance squared).

Then set (from the first constraint)

Then set (from the second constraint)

Then you have to solve the system of equations:

These become

Solve the first 3 equations in terms of x,y and z to get

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These are not all the same! Then you plug them in the last two equations and simplifying a bit, you get

Which is not very nice to solve.