lim
x→4 (√(2x+1)-3)/(√(2x-4)-2)
3條問題><
1)請問為何不可以 √(9)-3 / √(4)-2
=-3-3/-2-2
=3/2
2)若有根號,何時應取正/負
3)請解以上方程
中五m1 求指教..超難
2012-09-24 2:45 am
回答 (3)
2012-09-24 2:57 am
✔ 最佳答案
1 因為代入4後分母為√(2x - 4) - 2 = 02 在極限的計算中﹐如無特別說明﹐根號一定是取正的
3 lim(x->4) (√(2x + 1) - 3)/(√(2x - 4) - 2)
= lim(x->4) [1/√(2x + 1)]/[1/√(2x - 4)] (洛必達法則)
= (1/3)/(1/2)
= 2/3
2012-09-24 10:09 pm
√9 = 3
-√9 = -3
x^2 = 9 => x = 3 or -3
2012-09-24 14:09:20 補充：
√9 = 3
-√9 = -3
x^2 = 9 => x = 3 or -3
2012-09-24 14:09:36 補充：
√9 = 3
-√9 = -3
x^2 = 9 => x = 3 or -3
-√9 = -3
x^2 = 9 => x = 3 or -3
2012-09-24 14:09:20 補充：
√9 = 3
-√9 = -3
x^2 = 9 => x = 3 or -3
2012-09-24 14:09:36 補充：
√9 = 3
-√9 = -3
x^2 = 9 => x = 3 or -3
2012-09-24 3:55 am
If you haven't learn the L'Hospital rule, you may want to try rationalization.
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