Question

Suppose that the functions r and s are defined for all real numbers x as follows. r(x)=x+5 s(x)=3x+4 Write the expressions for (r*s)(x) and (r-s)(x) and evaluate (r+s)(-1) .

Answer 1

multiply, subtract, and add .... seems simple enough. Where is it your having problems?

Answer 2

i dont understand how to add subtract and all that.... can you please help me.. like do it and then show your work.. so i can do it next time??? PLEASE:)

Answer 3

i dont trust a "next time"

Answer 4

haha.. I'm doing a test with questions like these.. lol...

Answer 5

write out r-s for me so that i can see what it is your doing with them

Answer 6

I'm not sure thats the thing.... this is all confusing for me:P :(

Answer 7

its just replacing the function names with their defined equations, like if:

r = 7 and s = 3

what is: r-s?

just replace the names with the values

Answer 8

in this case, the values are expressions, so ...

(r-s)(x) = r(x) - s(x)

Answer 9

but r doesn't have a defined values.. it just is given the value that it says?

Answer 10

it doesnt have to have a defined value like 7 or 3, or -1/2; it is defined by its expression

just replace the names by the expressions and simplify the results is all its asking for

Answer 11

tell me, how is r(x) defined?

Answer 12

hey listen I'm sorry thanks for helping but i hate seeming dumb when people ask questions and i have no idea what the answer is.. thanks 4 trying

Answer 13

r(x)=x+5
s(x)=3x+4

using these definitions for r(x) and s(x); we contruct (r-s)(x) .... or better seen
as r(x)-s(x) by replacing them by their definitions

r(x) - s(x) ; lets replace r(x) with its definition of x+5

(x+5) - s(x) ; now lets replace s(x) with its given definition

(x+5) - (3x+4)

the rest is just doing the usual algebra stuff to simplify it

Answer 14

(r*s)(x) and (r+s)(x) follow the same concept

Answer 15

i simplified it to -2x+1 ?

Answer 16

yes, that is excellent simplifying :)

Answer 17

okayy! :) can you help me do the other two? idk how to put them in a equation or like you did up there!

Answer 18

i gave very explicit steps; can i at least see what it is that you try to work out? that way i can see where it is that you might be misunderstanding it at

Answer 19

hint; the on;y thing that changes in these is the operator in the middle ....

Answer 20

so i just substitute it out??

Answer 21

(r*s)(x) and (r+s)(x) with these and r(x)=x+5 s(x)=3x+4

Answer 22

yes

Answer 23

Okay soo for this : (r*s)(x) -> (x+5*3x+4)(x) ??

Answer 24

very close; the notation they are using seems to be the issue; think of the (x) as telling you that these are functions and not variables;

(r*s)(x) -> r(x) * s(x) -> (x+5)*(3x+4)

Answer 25

replace the * by a + to get (r+s)(x)

(r+s)(x) -> r(x) + s(x) -> (x+5) + (3x+4)

Answer 26

Ohhh okay!!! SO THAT ends up being: 4x+9?

Answer 27

(r+s)(x) ends up as: 4x+9 yes :)

Answer 28

and they want x to equal -1 in the addition setup; so we can find a real value for that by replacing x with a -1

Answer 29

ahh kinda got confused there...

Answer 30

hey I'm running out of time!! only 2 minutes left... i need an answer for each thingy!!!

Answer 31

pleaseee! i really appreciate this thoo

Answer 32

(r+s)(-1) is the question

(r+s)(-1) -> r(-1) + s(-1) -> (-1+5) + (3(-1)+4)

Answer 33

or since

(r+s)(x) -> 4x+9

then

(r+s)(-1) -> 4(-1)+9

Answer 34

so 5??

Answer 35

i would say 5 yes

Answer 36

for which one.. cuz i need 3 answers

Answer 37

i would assume its for the one we just did ....

Answer 38

do you have other (r+s)(-1) things hanging about?

Answer 39

one for (S*r)(x) =5
(r-s)(x)=-2x+1
(r+s)(-1)=4x+9
is this correct

Answer 40

your letting the timer cloud your judgements

no, that is not correct

Answer 41

omg.. I'm just writing that !! .... watever ill probably get it wrong anyways

Answer 42

good luck with the test overall tho :)

Answer 43

haha thanks:))