Question 81273
You are right f, g, and h are used for function notation (think of "f" for function). So f(x), g(x), and h(x) are functions. So if you have


{{{g(x)=x^2-2x}}}


and they want you to find {{{g(2c)}}} you simply plug 2c in for x


{{{g(2c)=(2c)^2-2(2c)}}}


To figure out which operation you perform, we must remember the order of operations. The common mnemonic is PEMDAS where it stands for:

Parenthesis
Exponents
Multiplication
Division
Addition
Subtraction



According to this order, multiplication has precedence over addition (you would perform multiplication first before addition). So this means we evaluate the exponent first


{{{g(2c)=4c^2-2(2c)}}} Square 2c to get {{{2^2*c^2=4c^2}}} note: you are squaring the entire term 2c. So 2 is squared also


Now multiply 


{{{g(2c)=4c^2-4c}}} Multiply 2 and 2c to get {{{2*2c=4c}}}


So g(2c) evaluates to 


{{{g(2c)=4c^2-4c}}}