Let f(x)=3x-7 and g(x)= -2x - 6, how do you find (f o g)(4)?

1 Answer
Oct 5, 2016

#(f@g)(4) = -49#

Explanation:

You can solve this in two ways:
#(1).# plugging the #4# into #g(x)# and then putting what you get from that in to #f(x)#
#(2).# plug #g(x)# into #f(x)# and then plug in the #4#

Option 1:

Plug #4# into #g(x)#:

#g(x) = -2(color(blue)(4))-6 = -8-6 = -14#

Then plug #g(x)# into #f(x)#:

#f(x) = 3(color(blue)(-14))-7 = -42-7 = -49#

Option 2:

Plug #g(x)# into #f(x)#:

#f(x) = 3(color(blue)(-2x-6))-7 = -6x-18-7 = -6x-25#

Finally plug #4# into our current #f(x)#:

#f(x) = -6(color(blue)(4))-25 = -24-25 = -49#