Question

Given the functions a(x) = 3x − 12 and b(x) = x − 9, solve a[b(x)] and select the correct answer below.
a[b(x)] = 3x2 − 21
a[b(x)] = 3x2 − 39
a[b(x)] = 3x − 21
a[b(x)] = 3x − 39

Answer 1

@Sammylemon @hero @Nnesha @Mehek14

Answer 2

please help ill medal and fan if i dont fan you already

Answer 3

The easiest way to explain is with an example....say you're evaluating for x=2. Because it's asking for a(b(x)), you plug in the x value into b(x) first. Whatever answer you get, you plug that in for x in the a(x) function.

Answer 4

ok??? :/

Answer 5

because they didn't give you a value for x, you have to plug in the entire b(x) function for every x value in the a(x) function. Once you've done that you simplify

Answer 6

ok what next??

Answer 7

so it'll look like this...
a(b(x))=3(x-9)-12

Answer 8

oh ok so next it would be 3x - 27 - 12

Answer 9

???

Answer 10

perfect, combine like terms and you're done.

Answer 11

x = -39?

Answer 12

wait now divide

Answer 13

nope...you're not solving for anything. go back to what you had before...3x-27-12

Answer 14

3x = -39
x = -13

Answer 15

again, not solving for anything....so when you combine like terms that's just a fancy way of saying do all addition and subtraction you can.

If you have 2x+3x-12 and you combine terms it would be 5x-12.

Answer 16

oh ok

Answer 17

so 3x-27-12...you can combine the -27 and the -12

Answer 18

again that would be -39

Answer 19

yup...put it with the first part of the equation and you have a(b(x))=3x-39

Answer 20

oh ok what now

Answer 21

that's it...in your original question it's the last choice in the list.

Answer 22

it's not set equal to anything so x is just a variable...it could be anything.

Answer 23

OH ITS D

Answer 24

YAYAYA YOUR AMAZING THANKS can you help with a couple more???

Answer 25

I'm a math/science teacher so I should know what I'm talking about :)

Answer 26

and sure, I have a little more time.