How do you know two lines are perpendicular? 1) Their slopes are equal

2) They look perpendicular

3) There is no way to tell

4) Their slopes are negative reciprocals

In a certain pentagon, the interior angles are a,b,c,d,e where a,b,c,d,e are integers strictly less than 180. ("strictly less than 180" means they are "less than and not equal to" 180.) if the median of the interior angles is 61 and there is only one mode, then what are the degree measures of all five angles?

Lena reflected this figure across the x-axis. she writes the vertices of the image as a'(−2, 8), b'(−5, 6), c'(−8, 8), d'(−4, 2).

Which shows one way to determine the factors of 4x3 + x2 – 8x – 2 by grouping?