Question

If f(2)=5 and f(-1)=-3, find a and b in function f(x)=ax+b.

Answer 1

You are given two points on the line and asked to find the equation of the line. So first find the slope.

Answer 2

If im to find the slope ... then what would be the coordinates. Unless the coordinates are (2,5) and (-1,-3)

Thats telling me f(x)=y ......

Answer 3

Yes. Those are the ordered pairs. Find the slope.

Answer 4

f(2) = 2a+b=5
f(-1)=-a+b=-3

Answer 5

then b+3 =a

Answer 6

@tianz2303 thats what I figure the answer would be !!!!! ..... but I have doubts ! :(

Answer 7

then you keep going like 2(b+3) + b=5

Answer 8

then b= -(1/3)

Answer 9

if a = b +3 then a= -(1/3) + 3 which is ?

Answer 10

a=8/3
so there you go :D

Answer 11

is it good?

Answer 12

Yeah! It seems good. Just ... a bit confusing. Im trying to break it down.

Answer 13

lol lemme put everything together

Answer 14

f(2) = 2a+b=5
f(-1)=-a+b=-3
then b+3 =a which would help us replace into first equation right? 2(b+3) + b=5
if you solve it 2b + 6 + b = 5 which will make 3b = -1 and finally b = - 1/3
if we go back to b+3 = a we replace our b value and we have a = 8/3
finally a=8/3 b= - 1/3

Answer 15

Totally ! Totally ! Tooooootaaaaally !!!!!!

I totally got it ! I did it and it came out easy !!! It's like finding the equation of a line just .... differently !!!

Answer 16

TOTALLY !!! Your awesome!

Answer 17

:D yaaay glad i helped!

Answer 18

Two points: (2,5) and (-1,-3)
Slope =
\[m=\frac{5-(-3)}{2-(-1)}=\frac{8}{3}\]
Point slope form:
\[y-y _{1}=m(x-x _{1})\]
Plug in the slope and either point:
\[y-5=\frac{8}{3}(x-2)\]
\[y=\frac{8}{3}x-\frac{1}{3}\]

Answer 19

There we go @Mertsj , totally on point ! I did it this way just seconds ago and my answers matched. I find that doing it @Mertsj way will be easier for me on my test! Awesome.

Thanks guys.

Answer 20

yw

Answer 21

haha sure i just go the easy way :/