1.solve -10<3x+5<-1 or 5x+6<-14
點解答覆係X<-2,而唔係-5<X<-2?
同埋X>-5可唔可以係答覆?
2. 0<角(唔識打符號)<360,y=2cos^2角 and y=5sin角+4
有幾多個相交點(INTERSECTION PT)
問數(關於不等式同NO OF ROOTS)
2013-04-05 6:50 pm
回答 (1)
2013-04-05 10:20 pm
✔ 最佳答案
以下是參考題解1 -10 < 3x + 5 < -1 or 5x + 6 < -14
-15 < 3x < -6 or 5x < -20
-5 < x < -2 or x < -4
畫數線後可以知道答案是x < -2
2 y = 2cos^2 x = 5sin x + 4
2cos^2 x = 5sin x + 4
2(1 - sin^2 x) = 5sin x + 4
2sin^2 x + 5sin x + 2 = 0
(2sin x + 1)(sin x + 2) = 0
sin x = -1/2 or sin x = -2 (捨去)
因此有2個交點
收錄日期: 2021-04-27 17:46:02
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20130405000051KK00096