Question

How did they get the equation in the solution to Example 1? f(x)=2x-6

http://www.themathpage.com/acalc/max.htm

Answer 1

By differentiating f(x) = x² − 6x + 5.

Answer 2

You missed the dash in your question :) f'(x)=2x-6

Answer 3

but how did they do that? can u explain further?

Answer 4

Have you been taught differential calculus?

Answer 5

To differentiate any function of x you multiply the coefficient of the x variable by the index then subtract 1 from the index hence x^2 becomes 2x^1 or simply 2x
-6x can be written -6x^1 therefore differentiating we get -6x^0 which is just -6