Using an ordered pair is a way of graphing a linear equation on a coordinate plane.
{(-1, 2), (0, 1), (1, 2), (4, 5)}.
The value of x in f(x)=4 is 4 because the f in f(x) is just 'naming' the equation, saying that x=a number, in this case, 4.
The missing angle is ninety degrees (Brainliest please)