Baileys rectangular dog pen for his irish setter must have an area of 300 square feet. also, the length must be 10 feet longer than the width. find the dimensions of the pen.

Area of rectangle = length × width
300 = (x+10) × x
300 = 10x + x^2
Now we have the equation y=x^2 + 10x - 300
We can factor this equation to get our zeroes, which are:
-5(1+sqrt(13)),
5(sqrt(13)-1)

We only use the positive zero because we can't have a negative dimension.

Your width would be:
5(sqrt(13)-1)

Your length would be:
5(sqrt(13)-1) + 10