Gọi UCLN(a,a+b)=d
Ta có:a chia hết cho d
a+b chia hết cho d
=>(a+b)-a chia hết cho d
=>b chia hết cho d
Mà a+b chia hết cho d
=>a chia hết cho d
=>d\(\in\)UC(a,b)
Vì UCLN(a,b)=1 nên d=1
Vậy \(\frac{a}{a+b}\) tối giản khi \(\frac{a}{b}\) tối giản
cho a,b thuc N*,a/b la phan so toi gian.chung to a/a+b la phan so toi gian
cho a va b la hai so nguyen to cung nhau chung minh rang a^2+b^2/a.b la phan so toi gian
Cho phan so: P = \(\frac{2n+7}{5n+2}\)(n thuoc Z)
a)Tim n thuoc z de P la phan so chua toi gian.
b)Tim n thuoc Z sao cho P la phan so toi gian.
cho A = 3N+2/6N+3
A TIM N DE a LA PHAN SO
b chung to A la phan so toi gian voi moi n thuoc N
tim a,b thuoc n va a/b la phan so toi gian biet a+b/a mu 2+a.b+b mu 2=49/1801
CMR : Neu a/b la phan so toi gian thi phan so a/a+b cung la phan so toi gian (b va a+b khac 0).
bai 1
a, chung to rang 2n+5/n+3, ( n thuoc N ) la phan so toi gian
b, tim gia tri nguyen cua n de B= 2n+5/n+3 co gia tri la so nguyen
bai 2
tim so tu nhien nho nhat sao khi chia cho 3 du 1 cho 4 du 2 cho 5 du 3 cho 6 du 4 va chia het cho 11
cach lam bai : chung to rang moi phan so co dang n+2015/n+2016 ( voi n thuoc N ) deu la phan so toi gian
tim phan so toi gian a/b (a,b thuoc N*)nho nhat de khi nhan a/b voi phan so 16/75 hoac 14/165 deu duoc moi tich la mot so tu nhien
