Can someone explain this question? i know the answer is t=0 but don't know why: (

Step-by-step explanation:

Your axis of symmetry is always going to be related to the x-point of your vertex. In this case, it looks like the vertex of the parabola is (0, 9). The vertex is the highest (or lowest) point of the parabola and is even on both sides. This means that, in order to be symmetrical, you would need to divide this parabola down "0."

for the friend request.

when a figure, such as triangle (xyz) is reflected over the line y = x to create x'y'z' the x-coordinates and y-coordinates of the original image (pre-image) will be reversed for the image. (e.g., (x, y) > (y, x)) this means that the pre-image position of the x- and y-coordinates switch places which in turn provides a mirror like image of the original xyz.  

i notice that when i draw a line segment from x to x', that the points are parallel from each other -- they are exactly across from each other and do not intersect with any other points.  

yes, think i would see the same characteristic if you drew the line segment connecting y with the reflecting line and then y' with the reflecting line because of the essence of reflections. because it is a mirror image, each point was effected the same way which leads me to conclude that they same would apply to y and y'.

3 is greater then both of those numbers