y=2x−1 is neither parallel nor perpendicular to line a; y=−2x+5 is parallel to line a; y=1/2x+7 is perpendicular to line a.
Step-by-step explanation:
Line a is written in slope-intercept form, y=mx+b, where m is the slope and b is the y-intercept. The slope of line a, the number in place of m, is -2.
Any line parallel to line a will have the same slope as line a, -2. The only line with this slope is y=-2x+5.
Any line perpendicular to this line will have a slope that is the negative reciprocal (this means the opposite sign and flipped upside down). This means that the slope of any line that is perpendicular to line a will have a slope of 1/2. The only line that has a slope of 1/2 is y=1/2x+7.