急!高一數學!部分分式法和雙重根號的化簡!

2014-05-03 6:11 pm
1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)=A/x(x+3)

求A=?

正解為3



雙根號化簡
大根號8-4小根號3=?

正解 根號6-根號2

回答 (13)

2014-05-03 8:09 pm
✔ 最佳答案
1/[x(x+1)]+1/[(x+1)(x+2)]+1/[(x+2)(x+3)]=A/[x(x+3)],求A=?
Sol
1/[x(x+1)]+1/[(x+1)(x+2)]+1/[(x+2)(x+3)]
=[(x+1)-x]/[x(x+1)]+[(x+2)-(x+1)]/[(x+1)(x+2)]+[(x+3)-(x+2]/[(x+2)(x+3)]
=[1/x-1/(x+1)]+[1/(x+1)-1/(x+2)]+[1/(x+2)-1/(x+3]
=1/x-1/(x+3)
=[(x+3)-x]/[x(x+3)]
=3/[x(x+3)]
A=3

雙根號化簡
√(8-4√3)?
Sol
√(8-4√3)
=√(8-2√12)
=√(6-2√12+2)
=√[(√6)^2-2√6*√2+(√2)^2]
=√[(√6-√2)^2]
=√6-√2


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2014-05-03 6:49 pm
(1)
X=1, 1/2 + 1/6 + 1/12 = A/4 A = 3

(2)
√((a+b)±2√ab) = √a±√b

√(8-4√3) = √(8-2√12) = √((6+2)-2√6x2) = √6 - √2


收錄日期: 2021-04-30 18:42:53
原文連結 [永久失效]:
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