What is the condition for a function y = f(x) to be a strictly increasing function.
x1>x2⇒f(x1)>f(x2)
We know from the definition, that a strictly increasing function is a function which increases on increasing the values of x. I.e. y values or f(x) values increases on increasing the x values. That is
x1>x2⇒f(x1)>f(x2)