Question 361915
write an equation for the line through the point (1,1) and perpendicular to the line 2x+y=9
2x+y=9
add -2x
y=-2x+9
compare this with slope  m of y = mx+b
m=-2 the slope
slope of perpendicular line = 1/2
...
equation of line 
y-y1=1/2(x-x1)
y-1=1/2(x-1)
2(y-1)=x-1
2y-2=x-1
add2
2y=x-1+2
2y=x+1
y=x/2 +1/2 is the line
...
{{{graph(300,300,-5,5,-5,10,(-2x+9),((x/2)+(1/2)))}}}