Hello everyone this is my first post!

Line A has the equation 3x + y = 7. Which of the following lines is perpendicular to Line A

RULE : If line 'a' with slope

m is perpendicular to say a line 'x' with slope

n , then m*n = -1

or conversely if two lines a and x with slopes m and n respectively, are such that their slopes m*n = -1 . Then we can say that a and b are perpendicular.

In the question above Line A has the equation 3x + y = 7. => y= (-3)x + 7 (which is of the form y=mx+b where m is the slope). therefore slope of line a is m=-3

so we need to find a line in the options that has a slope n= 1/3 ( since m*n=-1 (prerequisite for being perpendicular) =>-3*n=-1 =>n =1/3)

Almost all the equations below are of the form y=mx+b so its really easy to find the slope (lets call slope n)

(A) y = 3x + 4-------> n=3

(B) y = –3x – 6------->n=-3

(C) y = (1/3)x – 1------->n=1/3 (Eureka we found it!)

(D) y = (–1/3)x + 2------->n=-1/3

(E) y = (–7/3)x – 5-------> we don't really have to even check this..but sometimes I get a little paranoid and check it anyway n=-7/3

so the only option that works is option C

Give me a kudos if I helped you

Thanks