Hi lovely,
The answer you're looking for is 21.
RS is perpendicular to MN and PQ.
We can use the slopes of these lines to determine the answer.
Slope is given by the formula
m=.
Using the coordinates for M and N, we have:
m=.
Since PQ is parallel to MN, its slope will be as well, since parallel lines have the same slope.
Using the coordinates for points T and V in the slope formula, we have
m=.
This is not parallel to MN or PQ, since the slopes are not the same.
We can also say that it is not perpendicular to these lines; perpendicular lines have slopes that are negative reciprocals (they are opposite signs and are flipped). This is not true of TV either.
Using the coordinates for R and S in the slope formula, we have
m=. Comparing this to the slope of RS, it is flipped and the sign is opposite; they are negative reciprocals, so they are perpendicular.
13-9 = 4
4-4 = 0
0 divided by 2 = 0
2x = 0
x = 0
