Question

Let f(x) = x + 7 and g(x) = x – 2. What is f(x) • g(x)?

Answer 1

options:
x2 – 5x + 14

x2 + 5x – 14

x2 + 5x – 5

x2 + 9x + 5

Answer 2

well do you understand the notation f(x), g(x), s(x)...

Answer 3

no :/

Answer 4

You have to just multiply the two expressions..

Answer 5

\[f(x) \cdot g(x) = (x+7)(x-2) = ??\]

Answer 6

which method would I use to multiply the 2 expressions?

Answer 7

Have you heard about FOIL ??

Answer 8

oh yes, first, outer, inner last

Answer 9

Then go for it..

Answer 10

f(x), g(x), s(x)...

they all represent y, the out put of the function

so instead of saying

y = x + 7
y = x – 2

we replace y with the notation f(x), g(x), s(x), as if we wanted to talk about these functions it would be confusing to call them equation y

the x in brackets is the value we inputed in the function so if we wanted to talk about a specific point in a function we can just right f(2), instead of 2-2 (note this is more handy when dealing with ugly functions)

so just imagine f(x), g(x), s(x) as variables that represent the equations


so if we say

f(x) * g(x) we are just saying
(x + 7)(x – 2)


if we say

f(g(x)) we are just replacing x in x + 7 with x – 2

so we get

f(g(x)) = (x-2) + 7

Answer 11

hope that clears up the notation for you
remember

(x,f(x)) now instead of (x,y)

Answer 12

What did you get after multiplying them @brittneyy18rm

Answer 13

(x + 7)(x – 2) = x(x) + x(-2) + 7(x) + 7(-2)

Answer 14

after I multiplied them, I got x^2+5x-14 :)

Answer 15

Well Done..

Answer 16

thanks for your help!

Answer 17

Welcome dear.