Question 284608
Please help! A rectangular pool that is 20ft. long and 25ft. wide is to be surrounded by a concrete walk of uniform width. If the owner can only afford to pay for enough concrete to create a total walk area of 504 sq. ft., what is the width of this walk? 

let the width of the walk be x

The length of pool +walk will be 2x+25  ( width x on both sides of the pool)

The width will be 2x+20 

The area of pool +walk = (2x+20) * (2x+25)

The area of the pool = 20*25

(2x+20)(2x+25)- 500= 504

2x(2x+25)+20(2x+25)-500=504

4x^2+50x+40x+500-500=504

4x^2+90x-504=0

2x^2+45x-252=0

a=2, b= 45 * c= -252

b^2-4ac= 4041

x1= -45+sqrt4041 / 2*2

=4.64

x2=-45-sqrt4041 / 2*2

x2=-27.1

the width of the walk = 4.64 feet