To be perpendicular, the slopes must be negative reciprocals of one another, mathematically:
m1*m2=-1 our reference line has a slope of 1/2 so our perpendicular line must have a slope of:
m/2=-1
m=-2
The slope-intercept form of a line is y=mx+b so we have so far:
y=-2x+b, using point (2,-7) we can solve for b
-7=-2(2)+b
-7=-4+b
-3=b so our perpendicular line is:
y=-2x-3
If you MEANT what is the perpendicular line is POINT-SLOPE form then we know the slope is -2 and the point is (2,-7)...
POINT-SLOPE form is:
y-y1=m(x-x1), where m=slope and (x1,y1) is any point on the line then:
y--7=-2(x-2) (that would be the third one down in your choices)
...
"slope-intercept" form is: y=mx+b
"point-slope" form is: y-y1=m(x-x1)
"standard" from is: ax+by=c
