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Bài 1
1/Đ
2/Đ
3/S
4/Đ
5/Đ
6/S
7/S
8/Đ
9/S
10/S
Bài 2
1/<
2/>
3/<
4/>
5/>
6/<
7/<
8/<
9/<
10/<
\(\left(-\dfrac{5}{9}\right)+\dfrac{8}{18}+\left(-\dfrac{12}{11}\right)+\left(-\dfrac{4}{9}\right)+\dfrac{7}{15}\)
\(=\left[\dfrac{4}{9}+\left(-\dfrac{4}{9}\right)\right]+\left(-\dfrac{5}{9}\right)+\left(-\dfrac{12}{11}\right)+\dfrac{7}{15}\)
\(=-\dfrac{224}{495}\)
1: Rút gọn
a) \(-\dfrac{33}{51}=\dfrac{-33:3}{51:3}=\dfrac{-11}{17}\)
b) \(\dfrac{156}{-168}=\dfrac{-156}{168}=\dfrac{-156:12}{168:12}=\dfrac{-13}{14}\)
c) \(\dfrac{-75}{-100}=\dfrac{75}{100}=\dfrac{75:25}{100:25}=\dfrac{3}{4}\)
2: Quy đồng mẫu:
a) \(-\dfrac{3}{8}\) và \(\dfrac{5}{4}\)
MSC: 8
\(-\dfrac{3}{8}=\dfrac{-3}{8}\)
\(\dfrac{5}{4}=\dfrac{5\cdot2}{4\cdot2}=\dfrac{10}{8}\)
b) \(\dfrac{-7}{6}\) ; \(\dfrac{5}{12}\) và \(-\dfrac{5}{6}\)
MSC: 12
\(-\dfrac{7}{6}=\dfrac{-7\cdot2}{6\cdot2}=\dfrac{-14}{12}\)
\(\dfrac{5}{12}=\dfrac{5}{12}\)
\(\dfrac{-5}{6}=\dfrac{-5\cdot2}{6\cdot2}=\dfrac{-10}{12}\)
\(\frac{3}{4}+\frac{-1}{3}+\frac{-5}{18}\)
\(=\frac{5}{12}+\frac{-5}{18}\)
\(=\frac{5}{36}\)
a) - 7 < x < 0
x = -6 ; -5 ; -4 ; -3 ; -2; -1
b) 0 < x < 8
x = 1 ; 2; 3; 4; 5; 6; 7
c) 8 < x < -2
( không có x nào thỏa mãn điều kiện bài toán)
a) 5 : 3/4 - 4 4/5 : 3/4
= 5 . 4/3 - 24/5 . 4/3
= (5 - 24/5) . 4/3
= 1/5 × 4/3
= 4/15
b) -3/5 . 2/7 + (-3/7) . 3/5 + (-3/7)
= (-3/7) . (2/5 + 3/5 + 1)
= (-3/7) . 2
= -6/7
c) [(-4 2/7) . 7/11 + 7/11 . (5 1/3)] . 5 - 5 2/3
= (-30/7 . 7/11 + 7/11 . 16/3) . 5 - 17/3
= (-30/11 + 112/33) . 5 - 17/3
= 2/3 . 5 - 17/3
= 10/3 - 17/3
= -7/3
d) 5/39 . [(7 4/5) . (1 2/3) + (8 1/3) . (7 4/5)]
= 5/39 . (39/5 . 5/3 + 25/3 . 39/5)
= 5/39 . 39/5 . (5/3 + 25/3)
= 1 . 10
= 10
=
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