Question

If f(x) = 3x + 1, then f(a + h) - f(a) =

how do I do these problems??

Answer 1

how would you do:

f(3) - f(8) ??

Answer 2

do you even know how to define something like f(3) ??

Answer 3

You just have to substitute in place of 'x'

Answer 4

so I'd substiture the 3x+1 into what?

Answer 5

your not dubbing in the entire function, your subbing the x part of the function by the definition of x

Answer 6

*subbing in

Answer 7

spose we are given some function: g(x) ; what would this look like when x=2? replace x by 2 to get: g(2)

now spose we know the rule for g(x) is x+4; then g(2) is the value of the function when x=2; 2+4 = 6

Answer 8

Suppose*

Answer 9

in your setup, they ask you to sub in x=a and x=a+h, then subtract one from the other

Answer 10

^ Exactly.

Answer 11

does this make sense?

Answer 12

Yes it's starting to thank you

Answer 13

good, then lets try to work it thru with you;

lets define f(a) , which tells us that x=a. what do we get?

Answer 14

f(x) = 3x + 1 , i like to circle the x just to keep track of it

f(x) = 3(x) + 1 ; now, when x=a we get
f(a) = 3(a) + 1

f(x) = 3(x) + 1 ; now, when x=(a+h) we get
f(a+h) = 3(a+h) + 1

so, what is f(a+h)-f(a)?

( 3(a+h) + 1 ) - ( 3(a) + 1 )

and simplify

Answer 15

@amistre64 I do not think he knows what going in his class though.

Answer 16

thats fine, knowing takes time and practice :)

Answer 17

Thank you!

Answer 18

I guess so.

Answer 19

youre welcome, and good luck with it ;)