1 m=1000cm, so 21m=2100cm
1min=60sec
so 21 m/min=2100сm/60sec=35cm/sec
Y = 1/4x - 1....the slope here is 1/4....but for a perpendicular line we need a negative reciprocal slope...all that means is " flip " the slope and change the sign. 1/4....flip it....4/1.....change the sign....-4/1 or just -4. So our perpendicular line will have a slope of -4. The only one in ur answer choices with a slope of -4 is D.....so ur answer has to be D.
That looks hard... I can see the attachment tho<span />
