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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
A) 7/38 x 9/11 +7/38 x 4/11 -7/38 x 2/11
=7/38.(9/11+4/11-2/11)
=7/38
B) 5/31 x 21/25 + 5/31 x -7/10 - 5/31 x 9/20
=5/31.(21/25-7/10-9/20)
=5/31.(-31/100)
=-1/20
đây bạn
câu 1 bỏ dấu ngoặc rồi tính
( 36 + 79 ) + ( 145 _ 79 _ 36 )
\(=36+79+145-79-36\)
\(=\left(36-36\right)+\left(79-79\right)+145\)\
\(=0+0+145=145\)
10 _ [ 12 _ ( -9 _ 1 ) ]
\(=10-12-10\)
\(=10-10-12\)
\(=0-12=-12\)
( 38 _ 29 + 43) _ ( 43 + 38 )
\(=38-29+43-43-38\)
\(=\left(38-38\right)+\left(43-43\right)-29\)
\(=0+0-29=-29\)
271 _ [ ( -43 ) + 271 _ ( -17 ) ]
\(=271+43-271-17\)
\(=\left(271-271\right)+\left(43-17\right)\)
\(=0+26=26\)
- 144 _ [ 29 _ ( + 144 ) _ ( + 144 )]
\(=-144-19+144+144\)
\(=\left(-144+144+144\right)-19\)
\(=144-19=125\)
đợi mk lm tiếp câu 2 nha .
bài 2 tính tổng các số nguyên
- 18 < hoặc bằng x < hoặc bằng 17
\(\Rightarrow x\in\left\{-18;-17;-16;....;17\right\}\)
tổng \(x=-18+\left(-17\right)+\left(-16\right)+...+17=-18\)
- 27 < hoặc bằng x < hoặc bằng 27
\(\Rightarrow x\in\left\{-27;-26;-25;..;27\right\}\)
Tổng \(x=-27+\left(-26\right)+\left(-25\right)+...+27=0\)
a) 58.75+58.50-58.25
=58.(75+50-25)
=58.100
=5800
b) \(20:2^2-5^9:5^8\)
\(20:4-5\)
\(5-5=0\)
c)\(\left(5^{19}:5^{17}-4\right):7\)
\(\left(5^2-4\right):7\)
\(\left(25-4\right):7\)
\(21:7\)
=\(3\)
d) \(84:4+3^9:3^7+5^0\)
\(=21+3^2+1\)
\(=21+9+1\)
\(30+1=31\)
e) \(295-\left(31-2^2.5\right)^2\)
\(295-\left(31-4.5\right)^2\)
\(295-\left(31-20\right)^2\)
\(295-\left(11\right)^2\)
\(295-121\)
\(=174\)
f) \(11^{25}:11^{23}-3^5:\left(1^{10}\right)+2^3-60\)
\(11^2-243:1+8-60\)
\(121-243+8-60\)
\(-122+8-60\)
\(-114-60\)
\(=-174\)
a) \(12.79-64.37+12.21-36.37+12000\)
\(=\left(12.79+12.21\right)-\left(64.37+36.37\right)+12000\)
\(=\left[12\left(79+21\right)-37\left(64+36\right)+12000\right]\)
\(=12.100-37.100+12000\)
\(=1200-3700+12000\)
\(=9500\)
b) \(112.39+1237+112.61\)
\(=\left(112.39+112.61\right)+1237\)
\(=112\left(39+61\right)+1237\)
\(=112.100+1237\)
\(=11200+1237\)
\(=12437\)
c) \(35.762+351-35.662\)
\(=35\left(762-662\right)+351\)
\(=35.100+351\)
\(=3500+351\)
\(=3851\)
d) \(\frac{20}{4}-\frac{5^9}{5^8}=5-5=0\)
e) \(\left(\frac{5^{19}}{5^{17}}-4\right):7=\left(5^2-4\right):7=21:7=3\)
f) \(\frac{84}{4}+\frac{3^9}{3^7}+5^0=21+3^2+1=31\)