Question

If f(x)=7x and g(x)=3x+1, find (f o g)(x).
21x^2+7x
21x+7
21x+1
10x+1

Answer 1

i think its 21x+7 but im unsure @perl

Answer 2

(f o g) (x) is a special symbol, it means f ( g ( x))

Answer 3

lets calculate it

Answer 4

ok great

Answer 5

first plug in x into g(x)

f ( g ( x ) ) = f ( 3x + 1 )

Answer 6

when x goes into the g machine (g function) , out comes 3x + 1

Answer 7

now we put 3x + 1 into the f machine as the new input

Answer 8

ok heres where i usually get lost

Answer 9

ok so 3x+1 is the new input for f
now what is the rule for f machine?

Answer 10

f machine says f(x) = 7*x

treat 'x' as just a placeholder for input
so what f machine really says is
f ( input ) = 7 * input

Answer 11

so using '3x+1' as your input you have

f( 3x+1) = 7 * (3x + 1 )

Answer 12

Thanks for the help @perl

Answer 13

i like to draw the two functions as machines