Tìm số nguyên x
1 Tìm số nguyên x biết:
a, 4/3 . ( 1/6 - 1/2 ) < hoặc = x < hoặc = 2/3 .( -1/6 + 3/4)
b, ( 1/2 + 4/5 ).(3/13 - 8/13) < x< 1/5 . 10/7 + 2/3
c, 2/3 .( 1/3 + 3/4 -1/3) <hoặc = x/18 < hoặc = 7/3 ( 1/2-1/6)
d, ( 31/20 - 26/45 ) . -36/35 < x < ( 51/56 + 8/21 + 1/3 ) .8/13
2 Chứng tỏ rằng :
a, 1/10 . 1/11 + 1/11 - 1/12 +.......+ 1/20 .1 /21 > 1/20
b, ( 1 - 1/2 ).(1-1/3) ..........(1-1/10) <1/9
c, (1-1/5 ). ( 1-7/5) .( 1-3/5 ) . ( 1-9/5 )=0
a, 4/3 . ( 1/6 - 1/2 ) < hoặc = x < hoặc = 2/3 .( -1/6 + 3/4)
b, ( 1/2 + 4/5 ).(3/13 - 8/13) < x< 1/5 . 10/7 + 2/3
c, 2/3 .( 1/3 + 3/4 -1/3) <hoặc = x/18 < hoặc = 7/3 ( 1/2-1/6)
d, ( 31/20 - 26/45 ) . -36/35 < x < ( 51/56 + 8/21 + 1/3 ) .8/13
2 Chứng tỏ rằng :
a, 1/10 . 1/11 + 1/11 - 1/12 +.......+ 1/20 .1 /21 > 1/20
b, ( 1 - 1/2 ).(1-1/3) ..........(1-1/10) <1/9
c, (1-1/5 ). ( 1-7/5) .( 1-3/5 ) . ( 1-9/5 )=0