Question

The length of a rectangle is 8cm greater than twice its width. Find the dimensions if the area

is 42cm

Answer 1

Length
`14\ cm`

Width
`3\ cm`

Explanation:

Let

x-----> the length of rectangle

y ----> the width of rectangle

we know that

The area of rectangle is equal to

`A=xy`

`A=42\ cm^(2)`

so

`42=xy` ----> equation A

`x=2y+8` ---> equation B

substitute equation B in equation A and solve for y

`42=(2y+8)y\\ \\2y^(2)+8y-42=0`

Solve the quadratic equation by graphing

The solution is
`y=3\ cm`

see the attached figure

Find the value of x

`x=2(3)+8=14\ cm`

therefore

Length
`14\ cm`

Width
`3\ cm`