According to an x/y table, when x = –3, y = 21; when x = 4, y = –28; and when x = 5, y = –35.
when x = –3, y = 21
If it is a direct variation then it satisfies y = kx
Lets plug in -3 for x and 21 for y and find out k
y = kx
21= k (-3)
Divide by -3 on both sides
So k = -7
Lets check whether k = -7 for the other two set of values
when x = 4, y = –28,
-7 times 4 = -28
when x = 5, y = –35
-7 times 5 = -35
k =-7 satisfies all the set of values
So constant of variation k = -7
