Question

WILL GIVE MEDAL! I NEED HELP WITH THESE QUICK):

if f(x)=2x^2-4x and g(x)=5-2x, evaluate f(x)-g(x) for x=5

A.
15
B.
5
C.
35
D.
20






If f(x) = 5x – 3 and g(x) = 3x – 3, find f(x) – g(x).



A.
2x
B.
8x – 6
C.
2x – 6
D.
8x

Answer 1

Line up the like terms of these two functions and then combine the like terms, remembering that you are subtracting g(x) from f(x).

f(x) = 5x - 3
-g(x) = -3x -(-3)
----- = -------- = f(x) - g(x)

Answer 2

you just plug in the 2x^2 -4x into f(x) and 5-2x into G(x)
so it's (2x^2-4x)-(5-2x)
or 2x^2-4x-5-(-2x)
then you plug in 5 for all of the x's...

Answer 3

so for the second question my answer would be C?

Answer 4

Josh and I are proposing the same thing; I just find it helps some people to line up like terms in columns. Josh is right in that you plug in x=5 to obtain f(5)-g(5).

Kristina: Please show your work...support your choice with data.

Answer 5

all i did was subtracted 5-3 which equals 2 and 3-(-3) equals 6

Answer 6

im getting confused on how you explained it @Josh55 ):

Answer 7

when f(x)=2x^2-4x, that's saying you can just insert 2x^2-4x when you see f(x)
and the same with g(x) and 5-2x

Answer 8

so f(x)-g(x)
is really saying
(2x^2-4x) - (5-2x)

Answer 9

And when x=5 that means whenever you see an x you can just switch it with a 5. Does that help?

Answer 10

so I would subtract 2x^2 from 5?

Answer 11

K:

f(x) = 5x - 3
-g(x) = -3x -(-3)
----- = -------- = f(x) - g(x)

Finish this work, and then substitute 5 for x.

Answer 12

when you put 5 in the place of x then 2x^2 will turn into 2*5^2 which is 2*25 or 50

Answer 13

but for that problem I don't have to substitute anything @mathmale

Answer 14

K: Have you read the problem statement carefully?

if f(x)=2x^2-4x and g(x)=5-2x, evaluate f(x)-g(x) for x=5

Look at the last part of this sentence.

Answer 15

you gave me different numbers above lol @mathmale

Answer 16

okay so what would be the next step after we have 50 now? @Josh55

Answer 17

Are you sure I did that? If so, please show me where I gave you "different numbers."

Answer 18

can you see how you get 50?

Answer 19

if f(x)=2x^2-4x and g(x)=5-2x, evaluate f(x)-g(x) for x=5

I suggested that you add up like terms as follows:

f(x) = 5x - 3
-g(x) = -3x -(-3)
----- = -------- = f(x) - g(x)

Finish this work, and then substitute 5 for x.

Last time I checked, 5x-3x=2x, and so, if x=5, 2x=2(5) =10. and that's it. Where'd that 50 come from?

Answer 20

I don't mean to abandon you, but unfortunately I have another commitment to attend to now. Good luck. See you both again on OpenStudy.

Answer 21

the first problem is the one you substitute the second problem you do not. you keep giving me the second problem and saying i have to substitute @mathmale lol

Answer 22

yes i do.. @Josh55

Answer 23

ok :)

now do the exact same thing in

(2x^2-4x) - (5-2x)

Answer 24

and that'll give you the answer

Answer 25

2(5)^2-4(5)-(5-2(5) so just solve it like that?

Answer 26

@Josh55

Answer 27

and the answer would be 35 ?:)

Answer 28

Yes, BUT be sure to ADD 2(5) at the very end because there's a double negative

Answer 29

way to go

Answer 30

thank you so much!

Answer 31

you're welcome, keep it up!