First, find the slope for EF.
m= (x2-x1)/(y2-y1)
m= (-2-(-9)/(-1-(-5) Correct the signs. Two negatives= a positive.
m= (-2+9)/(-1+5)
m= 7/4
The slope of the perpendicular line would be the negative reciprocal.
'flip n switch' Flip the sign and switch the numbers.
m= -4/7
That is the slope of the perpendicular line.
I hope this helps!
~kaikers