Question

Please help Determine whether y varies directly with x. If so, find the constant of variation k and write the equation.

x y
7 11
8 13
9 15
10 17

Answer 1

x y
7 +4 = 11
+ +
1 2
= =
8 13
+ +
1 2
= =
9 15
+ +
1 2
= =
10 17

hope this will help you answering the question of your exercise right

Answer 2

The linear equation:
y = k x + b
We will use first two values and solve the system of equations:
11 = k * 7 + b / *(-1)
13 = k * 8 + b
---------------------
-11 = - k * 7 - b
13 = k * 8 + b
----------------------
2 = k
13 = 16 + b
b = 13 - 16 = -3
y = 2 x - 3 ( y varies directly with x )