Tim phan so a/b thoa man dieu kien 4/7 < a/b < 2/3 va 7a + 4b = 1994
tim phan so nho nhat co dang a/48 thoa man dieu kien 1/6<a/48<1/3
7. A= 4+3/x -1
a tim dieu kien de a la phan so
B tim dieu kien de a la so nguyen
Tim cac cap so nguyen thoa man dieu kien :
1/a+b/2=5/8
tim so tu nhien a co 3 chu so thoa man dieu kien khi chia a cho 140,350,700 co cung du la 7
tim cac so tu nhien a,b thoa man dieu kien \(\frac{11}{17}<\frac{a}{b}<\frac{23}{29}\)va 8b-9a=31
tim so tu nhin a be nhat thoa man dieu kien: 20/a< 4/5
20/a<4/5
=20/a<20/25
=20/26<20/25
=>a=26
\(\frac{20}{a}< \frac{4}{5}\)
\(\Rightarrow\frac{20}{a}< \frac{20}{25}\)
\(\Rightarrow\)\(a=\left\{26;27;28;29;30;31;...\right\}\)
\(\text{Mà a bé nhất nên a = 26}\)
\(\text{Vậy a = 26}\)
cho hai so tu nhien a va b thoa man dieu kien :10<a<b<15
1|khi a =12 hay tim b
2|Tìm a và b để hiệu b - a lớn nhất ,nhỏ nhất
tra loi ro rang va giai thiac nha minh cho nhieu like
1. khi a =12 thi b co the la 13 hoac 14
2.khi hieu b-a lon nhat thi b=14,a=11
hieu b-a be nhat thi ta co 3 truong hop
khi b bang 14 thi a =13
khi b bang 13 thi a bang 12
khi b bang 12 thi a =11
Tim cac so tu nhien A,B,C thoa man ca 2 dieu kien 20 nho hon A , nho hon B ,24 lon hon C lon hon B
\(20< A< B< C< 24\)
\(\Leftrightarrow A=21;B=22;C=23\)
Theo đề bài ta có :
20 < A < B < C < 24
=> A = 21
B = 22
C = 23
Cho 3 so duong a,b,c thoa man dieu kien : a+b+c=1. Chung minh rang
\(\sqrt{4a+1}+\sqrt{4b+1}+\sqrt{4c+1}< 5\)
Áp dụng BĐT Bunhia:
\(\sqrt{4a+1}+\sqrt{4b+1}+\sqrt{4c+1}\le\sqrt{\left(1+1+1\right)\left(4a+1+4b+1+4c+1\right)}\)
\(\Rightarrow\sqrt{4a+1}+\sqrt{4b+1}+\sqrt{4c+1}\le\sqrt{3.\left(4\left(a+b+c\right)+3\right)}=\sqrt{21}< \sqrt{25}=5\)
Vậy \(\sqrt{4a+1}+\sqrt{4b+1}+\sqrt{4c+1}< 5\)