Tính các tổng sau:

1, S=1-2+3_4+..+25-26

S =-1+3-5+7-...-53+55                       ( có 28 số hạng )

   = (-1+3)+(-5+7)+...+(-53+55)         ( có 28:2=14 nhóm )

   = 2+2+...+2

    = 2 . 14

     = 28

Á nhầm rùi xl bn nha

3 

S =-1+3-5+7-...-53+55     ( có 28 số hạng )

   = (-1+3)+(-5+7)+...+(-53+55)      ( có 28:2=14 nhóm )

   = 2+2+...+2

    = 2 . 14

     = 28

Bài 1:

1: =15+37+52-37-17=52-2=50

2: =38-42+14-25+27+15=62-42+29=20+29=49

Bài 1: Bỏ ngoặc rồi tính

3) (21-32) - (-12+32)=21-32-(-12)-32=21-32+12-32=-31

4) (12+21) - (23-21+10)=12+21-23+21-10=21

5) (57-725) - (605-53)=57-725-605+53=-1220

6) (55+45+15) - (15-55+45)=55+45+15-15+55-45=55+55=110

Bài 2: Tính các tổng sau một cách hợp lí

1) (-37) + 14 + 26 + 37=(-37+37)+(14+26)=0+40=40

2) (-24) +6 + 10 + 24=(-24+24)+(6+10)=0+16=16

3) 15 + 23 + (-25) + (-23)=(15-25)+(23-23)=-10+0=-10

4) 60 + 33 + (-50) + (-33)=(60-50)+(33-33)=10+0=10

5) (-16) + (-209) + (-14) + 209=(-16-14)+(-209+209)=-30+0=-30

6) (-12) + (-13) + 36 + (-11)=(-11-12-13)+36=-36+36=0

=15+37+52-37-17 =(37-37)+52+15-17 =0+52+15-17 =67-17 =50

(38 – 42 + 14) – (25 – 27 – 15) =38-42+14-25+27+15 =27 c. -(21 – 32) – (-12 + 32) =-21+32+12-32 =-9 d. -(12 + 21 – 23) - (23 – 21 + 10) =-12-21+23-23+21-10 =-22 e. (57 – 725) – (605 – 53) =57-725-605+53 =-1220 f. (55 + 45 + 15) – (15 – 55 + 45) =55+45+15-15+55-45 =110

1/10+2/10+3/10+4/10+5/10+6/10+7/10+8/10+9/10+55/10

=1+2+3+4+5+6+7+8+9+55 /10

=100/10

=10

Công lại :

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 55 / 10 

= 100 / 10

= 10

1/10+2/10=3/10+4/10+5/10+6/10+7/10+8/10+9/10+55/10

=1+2+3+4+5+6+7+8+9+55/10

=100/10

=10

ủng hộ mk nha mọi người người cảm ơn nhé

Bài làm :

\(A.\left\{\left[\left(3^2+1\right).10-\left(8:2+6\right)\right]:2\right\}+55-\left(10:5\right)^3\)

\(=\left\{\left[10.10-\left(4+6\right)\right]:2\right\}+55-\left(10:5\right)^3\)

\(=\left[\left(100-10\right):2\right]+55-2^3\)

\(=\left(90:2\right)+55-8\)

\(=45+55-8\)

\(=92\)

\(B.\left\{\left[\left(10-2.3\right).5\right]+2-2.6\right\}:2+\left(4.5\right)^2\)

\(=\left\{\left[\left(10-6\right).5\right]+2-12\right\}:2+20^2\)

\(=\left[\left(4.5\right)+2-12\right]:2+400\)

\(=\left(20+2-12\right):2+400\)

\(=10:2+400\)

\(=5+400\)

\(=405\)

Học tốt nhé

a)  {[(3² + 1).10 - (8:2 + 6)] : 2} + 55 - (10 : 5)³

= {[(9 + 1).10 - (4 + 6)] : 2} + 55 - 2³

= {[10.10 - 10] : 2} + 55 - 2³

= {[10(10 - 1)] : 2} + 55 - 8

= {[10.9] : 2} + 55 - 8

= 45 + 55 - 8 = 92

b) {[(10 - 2.3).5] + 2 - 2.6} : 2 + (4.5)²

= {[(10 - 6).5] + 2 - 12} : 2 + 20²

= {[4 . 5] + 2 - 12} : 2 + 400

= {20 + 2 - 12} : 2 + 400

= 10 : 2 + 400 = 5 + 400 = 405

\(A=\left\{\left[\left(3^2+1\right)10-\left(8:2+6\right)\right]:2\right\}+55-\left(10:5\right)^3\)

\(A=\left[\left(100-10\right)\frac{1}{2}\right]+55-8\)

\(A=45+55-8=92\)

\(B=\left\{\left[\left(10-2.3\right).5\right]+2-2.6\right\}:2+\left(4.5\right)^2\)

\(B=\left(20+2-12\right):2+400\)

\(B=405\)

\(\left\{\left[\left(3^2+1\right).10-\left(8:2+6\right)\right]:2\right\}+55-\left(10:5\right)^3\)

\(=\left\{\left[\left(9+1\right).10-\left(4+6\right)\right]:2\right\}+55-2^3\)

\(=\left\{\left[10.10-10\right]:2\right\}+55-8\)

\(=\left\{\left[100-10\right]:2\right\}+47\)

\(=\left\{90:2\right\}+47\)

\(=45+47\)

\(=92\)

Vậy...

{[(32 + 1 ) . 10 - ( 8:2 + 6 )]: 2} + 55 - (10 : 5)3

=\(\left\{\left[33.10-(4+6)\right]:2\right\}+55-2.3\)

=\(\left\{\left[330-10\right]:2\right\}+55-6\)

=\(\left\{320:2\right\}+49\)

=\(160+49\)

=209

B=2006 * 2008 -3 / 2005 + 2005 * 2008

B=(2005+1)* 2008 -3 / 2005 +2005 *2008

B=2005 * 2008 + 2008 -3 / 2005 +2005*2008

B=2005 * 2008 + 2005 / 2005 +2005 * 2008

B= 1

khi nào 2-1=3?