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1/ (a – b + c) – (a + c) = -b
a-b+c-a-c=-b
-b=-b
2/ (a + b) – (b – a) + c = 2a + c
a+b-b+a+c=2a+c
2a+c=2a+c
3/ - (a + b – c) + (a – b – c) = -2b
-a-b+c+a-b-c=-2b
-(b.2)=-2b
-2b=-2b
4/ a(b + c) – a(b + d) = a(c – d)
ab+ac-ab+ad=a(c-d)
ac-ad=a(c-d)
a(c-d)=a(c-d)
5/ a(b – c) + a(d + c) = a(b + d)
ab-ac+ad+ac=a(b+d)
ab+ad=a(b+d)
a(b+d)=a(b+d)
6/ a.(b – c) – a.(b + d) = -a.( c + d)
ab-ac-ab=ad=-a(c+d)
-ac+ad=-a(c+d)
-a(c+d)=-a(c+d)
a: \(=36:4+2\cdot25=9+50=59\)
b: \(=79\left(82+18\right)=79\cdot100=7900\)
c: \(=49-9-\left(4^2+2^2\right)\)
\(=40-16-4=40-20=20\)
d: \(=16+\left[400:\left(200-42-138\right)\right]\)
\(=16+400:20=16+20=36\)
a)\(3.5^2-16:2^2\)
=\(3.25-16:4\)
=\(75-4=71\)
b)\(2^3.17-2^3.14\)
=\(8.17-8.14\)
\(=8\left(17-14\right)\)
\(=8.3=24\)
c)\(15.141+59.15\)
=\(15\left(141+59\right)\)
\(=15.200\)=3000
d)17.85+15.17-120
\(=17\left(85+15\right)-120\)
=\(17.100-120\)
=\(170-120=50\)
e)\(20+[30-\left(5-1\right)^2]\)
\(=20+[30-\left(4\right)^2]\)
\(=20+\left(30-16\right)\)
\(=20+14=34\)
a, có vì số lẻ - số lẻ = số chẵn
b, có vì lẻ + lẻ - chẵn = chẵn
c, không vì 24a là số chẵn 10b cũng là số chẵn
a) 18 + 36 : 32
= 18 + 36 : 9
= 18 + 4
= 22
b) 23 . 81 + 23 . |-19|
= 2^3 . 81 + 2^3 . 19
= 2^3 ( 81 + 19 )
= 2^3 . 100
= 8 . 100
= 800
c) 2^3 . 5 - [ 6^2 : 4 + 3 ( 2^3 - 5 )]
= 8 . 5 - [ 36 : 4 + 3 ( 8 - 5 )]
= 40 - ( 36 : 4 + 3 . 3 )
= 40 - ( 9 + 9 )
= 40 - 18
= 22
a) \(\left(-0,75+\frac{1}{2}\right):\frac{4}{3}\)
\(=\frac{-1}{4}:\frac{4}{3}\)
\(=\frac{-3}{16}\)
b) \(\frac{5}{9}.\frac{2}{7}+\frac{5}{9}.\frac{5}{7}-\frac{8}{3}\)
\(=\frac{5}{9}.\left(\frac{2}{7}+\frac{5}{7}\right)-\frac{8}{3}\)
\(=\frac{5}{9}.1-\frac{8}{3}\)
\(=\frac{-19}{9}\)
c) \(7,5.1\frac{3}{4}-6\frac{2}{5}\)
\(=\frac{15}{2}.\frac{7}{4}-\frac{32}{5}\)
\(=\frac{269}{40}\)
a, 39.47 – 39.17
= 39.(47 – 17)
= 39.30
= 1170
b, 12.53 + 53.172 – 53.84
= 53.(12+172 – 84)
= 53.100
= 5300
c, 53.27 – 53.17
= 53.(27 – 17)
= 53.10
= 530
d, 33.59 + 59.151 – 59.84
= 59.(33 + 151 – 84)
= 59.100
= 5900
e, 29.63 – 29.13
= 29.(63 – 13)
= 29.50
= 1450
f, 91.2018 – 45.2018 – 46.2018
= 2018.(91 – 45 – 46)
= 2018.0
= 0