The answer is the fourth graph.
So what makes a function a function is that every input (x) has only one output (y). To test if a line is a function on a graph, you would use something called the "vertical line test". Move a vertical line across the graph, and if at any point there was more than one point on the vertical line it would not be considered a function. And the only graph that has no more than one point when moving a vertical line across the graph is the last graph.
The solution to this equation is x = 0 or x = 1
To find the solution, you use Desmos and enter x+2 in both one and 2^x+1 in box two. It will graph the lines for you and you take the x-coordinate of the two places where the lines overlap, and they overlap at (0,2) and (1,3).
Just borrow from the 7 and take the 1 to the 2 and that will make it as 12 so then you subtract 12 - 4 and the answer will be 1,180
Let 
. The tangent plane to the surface at (0, 0, 8) is
The gradient is
so the tangent plane's equation is
The normal vector to the plane at (0, 0, 8) is the same as the gradient of the surface at this point, (1, 1, 1). We can get all points along the line containing this vector by scaling the vector by 
, then ensure it passes through (0, 0, 8) by translating the line so that it does. Then the line has parametric equation
or 
, 
, and 
.
(See the attached plot; the given surface is orange, (0, 0, 8) is the black point, the tangent plane is blue, and the red line is the normal at this point)
