Find the value of f(15) if f(x) = 100x – 5x2.

this problem is to replace the variable (here "x" ) with a certain numerical value.

the given function is f(x) followed by the algebraic expression " 100x -5x^2 "

now u r asked to find f(15), mean u have to find the value of the "expression" with the numerical value "15" replacing "x"

so it looks like this:

f(x) = 100x -5x^2

f(15) = 100*15 - 5*(15)^2   [only "x" got replaced by it's numerical value "15"]

now u can calculate it

so

f(15) = 1500 - 5*225 = 1500 - 1125 = 375 (Ans.)

hope u got the basic idea.

feel free to ask if u have further queries.

all the best!