Determine whether the graphs of the two equations are perpendicular x-7y=4 and 21x+3y=11

Step-by-step explanation:

when multiplied together, the gradients of the 2 graphs should equal -1 (of they are perpendicular).

x-7y=4

-7y= -x + 4

y= -1/7 x + 4/7

21x+ 3y=11

3y=-21x+11

y=-21/3 x + 11/3

-21/3 * -1/7 = 1

when multipled together, the 2 gradients dont equal -1 therefore they are not perpendicular

unless I've made a mistake with the signs at some point haha