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A rectangular garden must have a perimeter of 150 feet and an area of at least 1200 square feet. Describe the possible lengths of the garden. Round your answers to the nearest foot.

Respuesta :

Answer: 51.86 and 23.14

Step-by-step explanation:

The rectangular garden must have a perimeter of 150 feet

Perimeter of rectangular garden =

2l + 2w=150 -----------1

The rectangular garden must have a perimeter of 150 feet and an area of at least 1200 square feet.

Area of rectangular garden =

l×w= 1200 feet^2 -----------2

From equation 2, l=1200/w

Put l=1200/w in equation 1

2× 1200/w + 2w = 150

(2400/w) +2w = 150

(2400+2w^2)/w =150

2400+2w^2= 150w

2w^2- 150w+2400=0

Using the general formula

w = [-b+-√(b^2-4ac)]/2a

a = 2, b =-150, c=2400

w =[--150+/-√(-150^2-4×2×2400)]/2×2

=[150+/-√(22500-19200)]/4

=[150+/-√3300)]/4

=(150+57.45)/4 or (150-57.45)/4

w= 207.45/4 or 92.55/4

w= 51.86 or w= 23.14

l = 1200/51.86 or l= 1200/23.14

l = 23.14. or l= 51.86

For an area of at least 1200ft^2

The dimensions are 51.86 and 23.14

The length of the garden is: l ≤ 23 ft or l ≥ 52ft

Let the length of the garden be represented by l

Let the width of the garden be represented by w

Perimeter, P =  150 feet

The perimeter of the rectangle  =  2(l  +  w)

2(l  +  w)   =   150

l   +  w    =  75......................(1)  

The area of the rectangle(A) = Length  x  width

A   =   lw

lw    ≤  1200...........(2)

Make w the subject of the formula in equation (1)

w   =  75  -  l...............(3)

Substitute equation (3) into equation (2)

(75 - l)(l)   ≤    1200

75l  -  l²  ≤   1200

0   ≤  l²  -  75l  +  1200

l²  -  75l  +  1200  ≥  0

Solving the quadratic inequality above:

l  ≥  51.86  or  l  ≤  23.13

Therefore, the length of the garden is: l ≤ 23 ft or l ≥ 52

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