Question

If the width of a rectangle is 3x, what is the length?

Answer 1

Given:

Area of the rectangle is defined as

`A(x)=3x^2+21x`

Width of the rectangle = 3x

Required: Length of the rectangle

Step-by-step explanation:

The formula to find the area of a rectangle is

Area = Length x Width

Plug the given values into the formula.

`\begin{gathered} 3x^2+21x=l\cdot3x \\ l=(3x^2+21x)/(3x) \\ =(3x^2)/(3x)+(21x)/(3x) \\ =x+7 \end{gathered}`

So, the length of the rectangle is x + 7.

Final Answer: The length of the rectangle is x+7.