Given #f(x) = 7x^2 - 5x#, #g(x) = 17x - 4# how do you find (fog)(6)?

1 Answer
Alan P.
May 16, 2018

#(fcircg)(6)=66,738#

Explanation:

#(fcircg)(x)# can be written as #f(color(blue)(g(color(red)x)))#

If #color(blue)(g(color(red)x))=17color(red)x-4#
then #color(blue)(g(color(red)6))=17 * color(red)6 -4 = color(blue)(98)#

and if #(fog)(color(blue)x)=f(color(blue)x)=7color(blue)x^2-5color(blue)x#
then #(fog)(color(blue)x)=f(color(blue)(g(color(red)x)))=7color(blue)(g(color(red)x))^2-5color(blue)(g(color(red)x))#
and
#color(white)("then ")(fcircg)(color(blue)x)=f(color(blue)(g(color(red)6)))=7 * color(blue)(98)^2 - 5 * color(blue)(98)=66738#
(I used a calculator for the last evaluation)

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