Here are the formulas you should remember about algebra:

• Writing f(x) is the same as y. This means that we can write a function as f(x) = 2x + 1 but we can also write it as y = 2x + 1

(cf)(x) = c.f(x)

(f + g)(x) = f(x) + g(x)

(f - g)(x) = f(x) - g(x)

(f.g)(x) = f(x).g(x)

(f/g)(x) = f(x) / g(x)