Given the equation:
[tex]C(x)=6x^2+90x[/tex]You know that "C" is the cost (in dollars) of producing a rectangular container, and "x" is the length of the side of the top and bottom that are squares.
In order to find the cost (in dollars) of producing a box container with a side of 8 feet, you need to set up that:
[tex]x=8[/tex]Then, you have to substitute that value of "x" into the equation and then evaluate:
[tex]\begin{gathered} C(8)=6(8)^2+90(8) \\ \\ C(8)=6(64)+720 \end{gathered}[/tex][tex]\begin{gathered} C(8)=6(64)+720 \\ \\ C(8)=384+720 \end{gathered}[/tex][tex]C(8)=1104[/tex]Hence, the answer is:
[tex]\text{ \$}1104[/tex]