what is the use of the formula of your pfp photo?
it's not a formula it is a function you put the value of x and get y f(x) = y okay? if the function is 2x +4x we can write it as: f(x) = 2x +3x now you put the value of x and get y f(2) = 2\*2 + 3\*2 f(2) = 4+ 6 = 10 got it? it means when the x is 2 y is 10 on graph for the function 2x+2x