想問下 一開始個102點整出黎架？
小雪冰 發表於 27-12-2013 09:22 http://www.nakuz.com/bbs/images/common/back.gif
係10^2 delta
iversonman 發表於 26-12-2013 11:25 http://www.nakuz.com/bbs/images/common/back.gif
delta= - 16p^2 + 36 要証佢<0 = 証16p^2-36>0
要証一個quadratic function>0 要consider呢二樣野
1.discriminant(delta)
2.quadratic function opens upward/downward(方向向上定向下)
由coefficient(系數) of x^2決定
當要証呢個16p^2-36>0
discriminant=0^2- 4(16)(-36)=2304 >0 所以同x-axis 相交
所以for all value of p不成立
所以証到個命題係錯
第一件事..吾係指delta<0 而係要寫"証delta<0"
第二- 16p2 + 36 = 16p2 -36 係錯的
第三 1.5(捨去) 佢話all value of p 所以吾應該捨去
最後 你好像無睇佢的方向(?)
dse加油 ( p2 + 4 )x2 + 4 - 10x = 0
Prove that for all value of p, the equation has no real roots
b^2-4ac < 0
(-10)^2-4(p^2+4)4 < 0
100-(16p^2+64) < 0
-16p^2+36 <0
p=-1.5 or 1.5
so when the value of p is -1.5 or 1.5 , the equation has no real roots.
我覺得大家誤解了題目
題目要在equation has no real roots的情況下 找出所有value of p
而非去prove that all value of p , the equation has no real roots呢件事
用F4思維解決F4問題好過庸人自擾 嗯 條問題出錯左
頁:
1
[2]