P= x^8 - x^5 + x^2 - x + 1
=x8-x5+(x-1/2)2+3/4
*Với x\(\ge\)0 =>x8\(\ge\)x5=>x8-x5\(\ge\)0
=>P=x8-x5+(x-1/2)2+3/4>0
*Với x<0=>x5<0 =>-x5>0=>x8-x5>0
=>P=x8-x5+(x-1/2)2+3/4>0
Vậy P luôn nhận giá trị dương
Ai tik cho mình thì người ấy may mắn cả năm!!!!!!!
à, chị hỏi ai đi , e chưa học ạ
ai ngang qua , kết bạn với mk nhé
P= x8 - x5 + x2 - x + 1
+) Có: x2 - x + 1 = x2 - 2.0,5x + (0,5)2 + 0,25
= ( x - 0,5 )2 + 0,25 > 0 ( áp dụng hằng đẳng thức ( a + b )2 = a2 +2ab + b2
+) Hiển nhiên x8 >= x5 nên x8 - x5 >=0
Do đó P > 0 hay P luôn nhận giá trị dương với mọi x.
P >0=>p luôn nhận giá trị dương với mọi x
Duyệt nhé!!!!!.......
TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT
TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT
P = x^8 - x^5 + x^2 - x + 1
= x8-x5+(x-1/2)2+3/4
*Với x > 0 => x8> x5=>x8-x5>0
=> P=x8-x5+(x-1/2)2+3/4>0
Vậy P luôn nhận gtrị dương
bai kho the minh moi hoc lop 5 thoi .
cac ban giai sai roi
neu x = 1/2 thi x^8 - x^5 < 0