Question

A rectangle has a length that is 9 feet less than four times its width. Its area is 90 square feet

Answer 1

Answer:

The length of rectangle is $15\ ft$

The width of rectangle is $6\ ft$

Step-by-step explanation:

Let

x-----> the length of rectangle

y----> the width of rectangle

we know that

The area of rectangle is equal to

$A=xy$

$A=90\ ft^{2}$

so

$90=xy$ -----> equation A

$x=4y-9$ -----> equation B

substitute equation B in equation A and solve for y

$90=(4y-9)y$

$4y^{2}-9y-90=0$

using a graphing calculator

The solution is

$y=6\ ft$

Find the value of x

$x=4y-9$  -----> $x=4(6)-9=15\ ft$