Lydia graphed adef at the coordinates d(-2,-1), e (-2, 2), and f (0.0). she thinks adef is a right triangle. is lydia's assertion correct? yes, the slopes of ef and df are opposite reciprocals. yes, the slopes of ef and df are the same. no; the siopes of ef and df are not opposite reciprocals. no, the siopes of ef and df are not the same

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.