Re: [請益] 一到數學題
※ 引述《goodlike (輝)》之銘言：
: 2. m為實數,y=x^2+(m-1)x+(m+7) 若y=0,有一根為1+根號3,則下列何者為真?
: A.m<-5 B.m<-4 C.m<-3 D.m>-2
: 這一題 我逆算回去對照原方程式發現 x項求得m=-1 常數項的m=-9....答案變AD= =
: 不知道怎解這題~~~謝謝各位了
: 以上兩題我都沒有解答(弄丟了)~~~~
題目給的m為實數，實係數方程式，若出現複數根，則複數根必共軛成對
若為有理係數方程式，出現無理根，則無理根必共軛成對
此題考的應該是這個概念，不可當做另一根為1-根號3
(不知道另一根當然就不可用根與係數)
因此只能將1+根號3代入會使等號滿足
移項去求m 為8根號3 減17 所以應該是-3.144左右 就選ｃ囉
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