which data set represents an increasing linear function?

Question

a) (1,-2),(3,1),(5,4),(7,7)
b) (1,1),(2,0),(3,-1),(4,-2)
c) (1,-3),(3,5),(5,11),(7,18)
d) (1,17),(2,15),(3,11),(4,3)

my answer: c) (1,-3),(3,5),(5,11),(7,18)

Answer 1

Answer a)

x1 = 1 , y1= - 2

x2 = 3 , y2 = 1

x3 = 5 , y3= 4

x4 = 7 , y4 = 7

x2 - x1 = 3 - 1 = 2

x3 - x2 = 5 - 3 = 2

x4 - x3 = 7 - 3 = 2

y2 - y1 = 1 - ( - 2 ) = 1 + 2 = 3

y3 - y2 = 4 - 1 = 3

y4 - y3 = 7 - 4 = 3

Numerically, y increases by 3 units for every 2 unit increase of x.

Answer 2

correct

http://www.wolframalpha.com/input/?i=plot+%281%2C-3%29%2C%283%2C5%29%2C%285%2C11%29%2C%287%2C18%29

Answer 3

Reiny

c)

isn't correct answer

In w o l f r a m a l p h a . c o m

type:

interpolate (1,-3),(3,5),(5,11),(7,18)

That is a cubic polynomial.

Answer 4

and

x4 - x3 = 7 - 5 = 2

Answer 5

sorry, did not register the "linear" part, and concentrated on the "increasing"

actually I think it is a),

the slope between any two points is 3/2

all points satisfy the equation
3x-2y=7

http://www.wolframalpha.com/input/?i=interpolate+%281%2C-2%29%2C%283%2C1%29%2C%285%2C4%29%2C%287%2C7%29+

Answer 6

Bosnian was right in his first post.

(think I will have a third cup of coffee to wake up)