Adata set contains three points, and two of the residuals are -10 and -20. what is the third residual?

The residuals of any data set should get added to zero. If there are three residuals (say A, B, and C) in any data set, then it could be written as A + B + C = 0.

Given are the two residuals -10 and -20 out of three point in a particular data set.

Let's assume A = -10 and B = -20, so that we could find third value C of the given data set.

We know A + B + C = 0

(-10) + (-20) + C = 0

(-30) + C = 0

C = 30

It means that third residual must be 30.

Hence, the final answer is 30.

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'.

a 360 degree rotation

step-by-step explanation: