Width = 15.616 feet, length is 25.616 feet.

Start with a sketch of a rectangle. Let ##x## be the width.

The length is 10 feet longer, so the length is ##(x + 10)##

The area is found from ## l xx w##, but this must be 400.

Make an equation in ##x## and solve it. Once you know the value of ##x## you can find y

##rArr ” ” x(x+10) = 400##

##x^2 +10x – 400 = 0 ” ” “factors are not obvious”##

Completing the square method probably easiest.

##x^2 + 10x + 25 = 400 + 25## ##(x + 5)^2 = 425## ##x + 5 = +-sqrt425)## ##x = sqrt425 – 5 ” ” or x = -sqrt425 – 5##

##x = 15.616 ” “or x = -25.6163##