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x | | x

———————— = = It's a wall, and the other three sides are fences.

y

1, because the fence is 30 meters long, one side is against the wall and the other three sides are surrounded by fences, so the other three sides add up to 30 meters, that is to say,

Y is parallel to one side of the wall, that is, Y+2x = 30, simplify Y = 30-2x, and then find the defined area. Since the wall is only 18m long, y cannot exceed 18m, that is, 30-2x 0, x< 15,

So the final answer is y = 30-2x (6

2, y = 30-2x, where y is the largest and x is the smallest, because 6

Or when y = y= 18m, the maximum is 18 = 30-2x and x = 6.

3, (the area of a rectangle is long by wide, the length is y = 30-2x, and the width is x)

Set the area of nursery as s,

Then s = xy = (30-2x) * x =-2x 2+30x (x 2 stands for the square of x).

Let s & gt=88, that is, -2x 2+30x > =88.

-2x^2+30x-88>； =0

-x^2+ 15-44>； =0

x^2- 15+44<； =0

The result of factorization is (x- 1 1) (x-4).

4 & lt= x & lt= 1 1

Because domain 6

Get 6

I think it's detailed enough. If you don't understand anything, you can continue to ask.