Answer:
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Step-by-step explanation:
5. its all of them so just write A, B, C, D, E, F, G
6. (equilateral) triangle, right triangle, diamond (?), parallelogram
7. C and E; A and B
8. not so sure about this one but i think its regular
9. its not a polygon because polygons have straight sides, and this figure does not.
10. the only polygon is C
pay attention in school, it'll help in the long run. even if it sounds boring, it will come in handy one day!!
hope this helped <33333
For this case we must follow the steps below:
step 1:
We place each of the given points on a coordinate axis
Step 2:
We join the AC points (represented by the orange line)
We join the BD points (represented by the blue line)
It is observed that the resulting figure after placing the 4 points on a coordinate axis, turns out to be a rhombus.
In addition, the blue and orange lines turn out to be perpendicular, that is, they have an angle of 90 degrees between them. This can be verified by finding the slopes of each of the two straight lines (blue and orange), which must be opposite reciprocal, that is, they comply: 
In this case, the slope of the orange line is
and that of the blue line is 
Then
, it is verified that they are perpendicular.
Thus, the conclusion is that ABCD is a rhombus and AC is perpendicular to BD.
Answer:
See attached image
Option D
84. Area of a triangle is (base x height) / 2
A rational expression is undefined when the denominator is zero.

is undefined when x=0 or x=2.
The answer is 3 (or 3.08)