Explain why the x-coordinates of the points where the graphs of the equations y = 4^−x and y = 2^x + 3 intersect are the solutions of the equation 4^−x = 2^x + 3.

The point where 2 lines intersect contain (x,y) coordinates that are equal for both equations.
By setting the 2 equations equal to each other, it is same as equating the 2 y-values, which we know they are equal at point of intersection.

Use a calculator basically