Where does the function, #f(x)=x^2-6x-7# intersect the function #g(x)=-12#?
They intersect at
A function is just a way to associate numbers with each others, according to a specified law, or rule. Imagine that you interrogate some robots giving numbers as input, and obtaining numbers as output.
So, two functions intersect if, when "asked the same question", they give the same "answer".
Your first function
The second function
So, the two functions can only intersect if, for some value
In formulas, we're looking for a value
If in particular we focus on the middle equality:
and from here you can use the quadratic formula to solve the equation, obtaining the two solutions