Question

A rectangle's sides are extended by 5 m. The new area of the figure is given by the expression: $a\left(x\right)=x^3+7x+8$. $x$ is the extension of sides. What is the new area?

• A. 168 square meters
• B. 158 square meters
• C. 178 square meters
• D. 198 square meters

Answer 1

The correct option is A

168 square meters

a(x) = $x^3+7x+8$

Plug in $x=5$

a(5) = $5^3+7\times 5+8$

a(5) = $125+35+8$

a(5) = 168 square meters