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a) 1/2 + 3/4 - (3/4 - 4 - 5)
= 1/2 + 3/4 - 3/4 + 4 + 5
= (3/4 - 3/4) + (4 + 5) + 1/2
= 0 + 9 + 1/2
= 19/2
b) [9/16 + 8/(-27)] - (19/27- 7/16 - 2)
= 9/16 - 8/27 - 19/27 + 7/16 + 2
= (9/16 + 7/16) + (-8/27 - 19/27) + 2
= 1 - 1 + 2
= 2
c) -5/8 . [4/9 + 7/(-12)]
= -5/8 . (-5/36)
= 25/288
d) 7/10 . (-3/5) + 7/10 . (-2/5) - (-3/10)
= 7/10 . (-3/5 - 2/5) + 3/10
= 7/10 . (-1) + 3/10
= -2/5
e) -3/7 . 5/9 + 4/9 . (-3/7) + 2 3/7
= -3/7 . (5/9 + 4/9) + 17/7
= -3/7 . 1 + 17/7
= 2
f) 8 2/7 - (3 4/9 + 4 2/7)
= 8 + 2/7 - 3 - 4/9 - 4 - 2/7
= (8 - 3 - 4) + (2/7 - 2/7) - 4/9
= 1 - 4/9
= 5/9
h) 3.(-1/2)² - (4/5 + 8/15) : 5/6
= 3.1/4 - 4/3 : 5/6
= 3/4 - 8/5
= -17/20
Câu 1:
16 - 18|x| = - 8 - 14|x|
18|x| - 14|x| = 16 + 8
4|x| = 24
|x| = 24 : 4
|x| = 6
x = - 6 hoăc x = 6
Vậy x ∈ {-6; 6}
e) 15-3|4x +2| = 3
3|4x + 2| = 15 - 3
3|4x + 2| = 12
|4x + 2| = 12 : 3
|4x + 2| = 4
4x + 2 = -4 hoặc 4x + 2 = 4
Th1: 4x + 2 = - 4
4x = - 4 - 2
4x = - 6
x = - 6/4
x = - 3/2
Th2: 4x + 2 = 4
4x = 4 - 2
4x = 2
x = 2/4
x = 1/2
Vậy x ∈ {- 3/2; 1/2}
Câu 1:
16 - 18|x| = - 8 - 14|x|
18|x| - 14|x| = 16 + 8
4|x| = 24
|x| = 24 : 4
|x| = 6
x = - 6 hoăc x = 6
Vậy x ∈ {-6; 6}
a: \(A=\dfrac{15}{4}-\dfrac{9}{4}=\dfrac{6}{4}=\dfrac{3}{2}\)
b: \(B=\dfrac{-3}{2}\cdot\dfrac{7-5\cdot4}{3}=\dfrac{-13}{-2}=\dfrac{13}{2}\)
c: \(C=\dfrac{-21}{10}\left(1-\dfrac{3}{4}\right)-\dfrac{3}{4}\)
\(=\dfrac{-21}{10}\cdot\dfrac{1}{4}-\dfrac{3}{4}\)
\(=\dfrac{-21}{40}-\dfrac{30}{40}=\dfrac{-51}{40}000000997\)
d: \(D=\dfrac{-2}{3}+\dfrac{-12}{5}-3=\dfrac{-10-36-45}{15}=\dfrac{-91}{15}\)