đề thi hả bn

ko, chỉ là btvn thôi nhé, mình nhầm

a: (a-b)+(c-d)-(a+c)

=a-b+c-d-a-c

=-b-d=-(b+d)

b: (a-b)-(c-d)+(b+c)

=a-b-c+d+b+c

=a+d

c: (a+b-c)+(a-b)-(a-b-c)

=a+b-c+a-b-a+b+c

=a+b

d: -(a-b-c)+(-a+b-c)-(-a+b+c)

=-a+b+c-a+b-c+a-b-c

=-a+b-c=-(a-b+c)

Bài 5 :

a) x + (-13) = -144 - (-78)

x + (-13) = -36

x = -36 - (-13)

x = - 23

b) x + 76 = 58 - (-16) 

x +76 = 74

x = 74 - 76 = -2 

b: \(\Leftrightarrow n+1\in\left\{1;-1;2;-2;4;-4\right\}\)

hay \(n\in\left\{0;-2;1;-3;3;-5\right\}\)

c: \(\Leftrightarrow n+2\in\left\{1;-1;5;-5\right\}\)

hay \(n\in\left\{-1;-3;3;-7\right\}\)

d: \(\Leftrightarrow n+2\in\left\{1;-1;2;-2;4;-4\right\}\)

hay \(n\in\left\{-1;-3;0;-4;2;-6\right\}\)

a: \(\Leftrightarrow n-1\in\left\{1;-1;5;-5\right\}\)

hay \(n\in\left\{2;0;6;-4\right\}\)

a)12/23

   18/39

    24/52

   30/65 

   36/78

   42/91

b) 45/-21

    75/-35

Số số hạng của dãy số là:

\(\frac{999-1}{2}+1=\frac{998}{2}+1=\frac{1000}{2}=500\) (số)

-1-3+5+7-9-11+13+15-...-993-995+997+999

=(-1-3+5+7)+(-9-11+13+15)+...+(-993-995+997+999)

=8+8+...+8

\(=8\cdot\frac{500}{4}=500\cdot2=1000\)

a: (326-43)+(174-57)

=326-43+174-57

=500-100=400

b: (351-875)-(125-149)

=351-875-125+149

=500-1000

=-500

c: \(-415-\left\lbrace-215-\left\lbrack-115-\left(-315-2016\right)\right\rbrack\right\rbrace\)

\(=-415-\left\lbrace-215-\left\lbrack-115+315+2016\right\rbrack\right\rbrace\)

=-415+215+(200+2016)

=2016

d: [461+(-78)+40]+(-461)

=(461-78+40)-461

=461-38-461

=-38

e: -323+[(-874)+564-241]

=-323-241+564+(-874)

=0-874

=-874

f: [(-59)+71]-[-83-(-95)]

=-59+71-(-83+95)

=12-12

=0

e: Để 4n+1/3n-1 là số nguyên thì \(12n+3⋮3n-1\)

\(\Leftrightarrow3n-1\in\left\{1;-1;7;-7\right\}\)

hay \(n\in\left\{0;-2\right\}\)