Ta có:
\(\frac{1}{2^2}< \frac{1}{1.2},\frac{1}{3^2}< \frac{1}{2.3},...,\frac{1}{45^2}< \frac{1}{44.45}.\)
\(\Rightarrow A=\frac{1}{2^2}+\frac{1}{3^2}+...+\frac{1}{45^2}< \frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{44.45}.\)
\(\Leftrightarrow A< 1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{44}-\frac{1}{45}=1-\frac{1}{45}< 1.\)
Lại có A>0
=>0<A<1
=>A không là số nguyên
Cho minh hoi bai nay. Chi can tra loi 1 cau cung duoc! Tick cho ai tra loi som nhat, day du nhat.
1. Cho so huu ti y=2a-1/-3. Voi gia tri nao cua a thi y la so duong, y la so am, khong phai so duong cung phai so am?
2. Cho so huu ti x=a-5/a (a khac 0). Voi gia tri nao cua a thi x la so nguyen?
3. Cho so huu ti x=a-3/2a (a khac 0). Voi gia tri nao cua a thi x la so nguyen?
Trong cac cau sau day , cau nao dung , cau nao sai ?
a) Neu a la so nguyen thi a cung la so thuc .
b) Chi co so 0 khong la so huu ti duong va cung khong la so huu ti am .
c) Neu a la so tu nhien thi a khong phai la so vo ti .
a)Cho vi du ve 1 don thuc ,1 da thuc nhung khong phai la don thuc ,2 don thuc dong dang voi nhau ,da thuc 1 bien
b)Hay viet 1 don thuc dong dang voi don thuc don thuc xy\(^3\) sao cho tai x=-1 y=2 gia tri cua don thuc do la so nguyen duong nho hon 10
CMR
\(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{16}\) khong la 1 so nguyen
Cho so :
\(y =\frac{2a-1}{-3}\)
voi gia tri nao cua a thi
a) y la so duong
b) y la so am
c) y khong la so duong cung khong phai so am
C/M gia tri bieu thuc sau khong phai la mot so nguyen
\(\frac{a}{2016-c}+\frac{b}{2016-a}+\frac{c}{2016-b}\)
cho M(x) =-x^4-2x^3+3x^2 so nao duoi day khong phai la nghiem cua M(x)
1. -1
2. -3
3. 1
.4. 0
cho A = 1 - 3/4 + (3/4)^2 - ...-(3/4)^2009 + (3/4)^2010
chung to A k phai la so nguyen
Cho Sn=(1^2-1/1)+(22-1/22)+(32-1/32)+.......+n2-1/n2
CMR Snko phai la so nguyen
