Which graphs have domains that contain all real numbers ?

Graph 1 represents a linear function with a domain containing all real numbers, as any input substituted into the equation or function will produce a corresponding output. The arrows on the opposite ends of the line represents the infinite input values that have its corresponding output values.

Graph 2 represents a quadratic function with a domain containing all real numbers, as it does not have any constraints in terms of input values. As it opens up, the graph of the parabola infinitely widens (horizontally).

Graph 3 represents an absolute value function with a domain containing all real numbers. Similar to the explanation for graph 2 on quadratic functions, the downward-facing graph of the given absolute value function widens infinitely horizontally, as it does not have any constraints on input values.