A rectangular garden is 4m wide and 7m long. If its width and length are each increased by x m, then the new area of the garden will become twice its original area.
a)Find the new area of the garden in terms of x.
b)What are the new width and the new length if the garden?
(corr to 3s.f.)
f,4 mathz,,,area of garden.
2008-09-24 9:40 pm
回答 (1)
2008-09-24 9:54 pm
✔ 最佳答案
a)(4+x)(7+x)= x2+11x+28
x2+11x+28 = 2*4*7
x2+11x+28 = 56
x2+11x-28 = 0
x = (-11+root(121+112))/2 or(-11-root(121+112))/2
= 2.13 or -13.1(rej)
2008-09-24 13:54:39 補充：
b)
x2+11x+28 = 2*4*7
x2+11x+28 = 56
x2+11x-28 = 0
x = (-11+root(121+112))/2 or(-11-root(121+112))/2
= 2.13 or -13.1(rej)
2008-09-24 18:12:15 補充：
the new width
= 2.13+4 = 6.13m
the new length
= 2.13+7 = 9.13m
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