Thread: [SOLVED] need a lil help figuring out a problem

Supposed the point (2,4) is on the graph of y=f(x). Find a point on the graph of the given function

1) y=f(x+1)
a)(2,3)
b) (1,4)
c) (2,5)
d) (3,4)

2)y=f(x)+8
a) (2,-8)
b) (-6,4)
c) (2,12)
d) (10,4)

Im not looking for the answer, but rather how to solve the problems. I can't find a similar one in my book.

Originally Posted by ninobrn99

Supposed the point (2,4) is on the graph of y=f(x). Find a point on the graph of the given function

1) y=f(x+1) Mr F says: Substitute x = 1 and what have you got ....?
a)(2,3)
b) (1,4)
c) (2,5)
d) (3,4)

2)y=f(x)+8 Mr F says: Substitute x = 2 and what have you got ....?
a) (2,-8)
b) (-6,4)
c) (2,12)
d) (10,4)

Im not looking for the answer, but rather how to solve the problems. I can't find a similar one in my book.

..

You only know f(2) so you must turn whatever you have into '2'. That is the point of mr fantastic's suggestion: if x= 1, then x+1= 2 so f(x+1)= f(2).

sorry, im still not getting it. Maybe I need the problem worked so I can see the steps. I was up till 3am working on this stuff

Originally Posted by ninobrn99

sorry, im still not getting it. Maybe I need the problem worked so I can see the steps. I was up till 3am working on this stuff

x = 1: y = f(1 + 1) = f(2). But you know f(2) = 4. Therefore a point on the graph of y = f(x+1) is (1, 4).

Try the other one now.

Originally Posted by mr fantastic

x = 1: y = f(1 + 1) = f(2). But you know f(2) = 4. Therefore a point on the graph of y = f(x+1) is (1, 4).

Try the other one now.

Im not sure if I'm making sense, but here's what Im getting:

f(x) is a constant which is why when x=1, y=4 and when x=2, y=4

since the next problem is linear, [f(2)=4] + 8 therefore, the answer to
f(x)+8 is (2,12)

Is that at all close?

No one has told you that f(1)= 4! mr fantastic told you that if x= 1 then f(x+1)= f(2)= 4. That tells you nothing about f(1).

You are told initially that f(2)= 4. That is the only value of f you know and so is the only value you [b]could[\b] get.

You are however correct that f(2)+ 8= 4+ 8= 12 because, again, you are working with f(2).

Thank you both. It's starting to make sense. I've got three word problems left, I'll try my best to knock them out on my own, if not, Im posting back up