Write a function rule for the area of a rectangle whose length is 3 ft more than its width. What is the area of the rectangle when its width is 8 ​ft?

Answer 1

A = area

l = length

w = width

Area formula is

A = l * w

but l = w + 3. Length is 3 ft more than width.

So,

A = (w+3) * w

A(w) = w² + 3w. This is the area as a function of the width w in ft.

For w = 8 ft,

A(8) = 8² + 3*8

A(8) = 64 + 24 = 88 ft²

The area of the rectangle is 88 ft² when the width is 8 ft.

Note: Make sure your units are all the same for a problem like this before multiplying or adding terms. Convert units to make them the same if necessary. When the units agree, you can carry out simple operations without showing them. But record your final answer to the correct units.

Answer 2

Area of a rectangle is width×length. Length in this case is the width + 3.

Let w be the width.

A(w) = w(w+3) = w²+3w

A(8) = 8²+3(8) = 64 +24 = 88