Answer:
Find the area of the circle then divide by two
Step-by-step explanation:
Because a rectangular pyramid's base is square, the cross section would be as well
Lagrange multipliers:







(if

)

(if

)

(if

)
In the first octant, we assume

, so we can ignore the caveats above. Now,

so that the only critical point in the region of interest is (1, 2, 2), for which we get a maximum value of

.
We also need to check the boundary of the region, i.e. the intersection of

with the three coordinate axes. But in each case, we would end up setting at least one of the variables to 0, which would force

, so the point we found is the only extremum.
F(X) means plug in te number within the parenthesis for the given function. It's simply an equation expressed through different notation. In this case it asks you to plug in two, so you do:
-3(2)+4 = f(2)
That means that f(2)=-2.