If #s(x) = 2-x and t(x) =3x# , what is # (s * t)(-7)#?

1 Answer
Nov 29, 2017

#-189#

Explanation:

#"establish "(s*t)(x)=s(x)xxt(x)#

#=3x(2-x)=6x-3x^2#

#"to evaluate "(s*t)(-7)#

#"substitute x = - 7 into "(s*t)(x)#

#(s*t)(color(red)(-7))=(6xxcolor(red)(-7))-(3xxcolor(red)((-7)^2))#

#color(white)(xxxxxxx)=-42-147=-189#