Question

find a function rule
x -2 , -1 , 0 , 1 , 2
y 9 , 4 , -1 , -6 , -11

please help!!

Answer 1

first make a graph and plot any three of the points

Answer 2

ok

Answer 3

then?

Answer 4

we see if it is a straight line, is it?

Answer 5

ok hold on

Answer 6

yes

Answer 7

awesome, so we know its a line. that means we can make a function starting from the standard function of a line:

y = mx+b

do you remember how to find the slope between two points? if so, pick any two points and find the slope, if not, just tell me?

Answer 8

-2 , 2

Answer 9

then

Answer 10

hello

Answer 11

to find the slope I do,

the change in y of two points
divide by
the change in x of two points:

i'll pick points, (-2, 9) (-1, 4)
looking at the y values I have 9 and 4, the change to go from 9 to 4 is -5
looking at the x values I have -2 and -1, the change to go from -2 to -1 is 1

so my slope is -5/1 or -5

now we know m = -5

lets plug in any point given to us, and the value of m in to the equation
y = mx+b
and solve for b

Answer 12

you sent me a message, am I not helping you the way you would like?

Answer 13

no I thought you went away ! sorry!

Answer 14

^_^

Answer 15

ok, let me check

Answer 16

How do I solve b?

Answer 17

what point did you pick from what they gave us in the problem and i'll show you?

Answer 18

(0, -1) and (1, -6)

Answer 19

we only need 1 points, so i'll use (0, -1)

y = mx+ b
m = -5
x = 0
y = -1
-1 = -5*0 + b

solve for b

Answer 20

ok

Answer 21

is b 0?

Answer 22

-1 = -5*0 + b
-1 = 0 + b
-1 = b

Answer 23

ohh, so b is -1?

Answer 24

yep!

so we are basically done after this next step. the problem wanted us to find the function of the points. So, we found what m equals and what b equals.

just plug in m and b into the equation
y = mx+b

and the equation becomes the answer

Answer 25

oh, thanks!!

Answer 26

^_^