Need to write an equation in slope intercept form to the line perpendicular to 7x-2y=9 passing through (1,-2)

Question

confused by perpendicular.  Do I put into slope intercept form first

Answer 1

Take the first equation and put it into slope-intercept form first:

 

7x - 2y = 9

-2y = -7x + 9

y = (7/2)x + (9/2)

 

The slope of the original line is therefore 7/2.

 

The perpendicular has a slope that is the negative reciprocal; the slope of the perpendicular is -2/7.

 

Now the equation of your line is:

 

y = (-2/7)x + b

Use the point to solve for b:

 

-2 = (-2/7)*1 + b

b = -2 + (2/7) = -12/7

 

Therefore, your equation is y = (-2/7)x - (12/7)