a) 35 x 34 + 35 x 86 + 65 x 75 + 65 x 45 

= 35 x ( 34 + 86 ) + 65 x ( 75 + 45 )

= 35 x 120 + 65 x 120

= 120 x ( 35 + 65 )

= 120 x 100

= 12 000

Bạn có thể trả lời phần thứ hai không

50 tan

1)

\(\left(a\right)37+397+3997+39997\)

\(=40-3+400-3+4000-3+40000-3\)

\(=\left(40+400+4000+40000\right)-\left(3+3+3+3\right)\)

\(=44440-12=44428\)

\(\left(b\right)298+2998+29998+299998\)

\(=300-2+3000-2+30000-2+300000-2\)

\(=\left(300+3000+30000+300000\right)-\left(2+2+2+2\right)\)

\(=333300-8=333296\)

\(\left(c\right)9+99+999+9999+99999\)

\(=10-1+100-1+1000-1+10000-1+100000-1\)

\(=\left(10+100+1000+10000+100000\right)-\left(1+1+1+1+1\right)\)

\(=111110-5=111105\)

2)
\(\left(a\right)\left(2+4+6+...+2002+2004+2006\right)-\left(1+3+5+...+2001+2003+2005\right)\)

\(=\left(2-1\right)+\left(4-3\right)+\left(6-5\right)+...+\left(2002-2001\right)+\left(2004-2003\right)+\left(2006-2005\right)\)

\(=1+1+1+...+1+1+1\)( 1003 số 1 )

\(=1003\)

\(\left(b\right)88-87+86-85+84-83+...+6-5+4-3+2-1\)

\(=\left(88-87\right)+\left(86-85\right)+\left(84-83\right)+...+\left(6-5\right)+\left(4-3\right)+\left(2-1\right)\)

\(=1+1+1+...+1+1+1\)( 44 số 1 )

\(=44\)

\(\left(c\right)100-98+96-94+92-90+...+12-10+8-6+4-2\)

\(=\left(100-98\right)+\left(96-94\right)+\left(92-90\right)+...+\left(12-10\right)+\left(8-6\right)+\left(4-2\right)\)

\(=2+2+2+...+2+2+2\) ( 25 số 2 )

\(=50\)

3)

\(\left(a\right)360-357+354-351+348-345+...+312-309+306-303+300-297\)

\(=\left(360-357\right)+\left(354-351\right)+\left(348-345\right)+...+\left(312-309\right)+\left(306-303\right)+\)\(\left(300-297\right)\)

\(=3+3+3+3+3+3+3+3+3+3+3=33\)

\(\left(b\right)2006-1-2-3-4-...-47-48-49-50\)

\(=2006-\left(1+2+3+4+...+47+48+49+50\right)\)

\(=2006-\frac{\left(50+1\right)\left[\left(50-1\right)+1\right]}{2}\)

\(=2006-1275=731\)

\(\left(c\right)280-276+272-268+264-260+...+216-212+208-204+200-196\)

\(=\left(280-276\right)+\left(272-268\right)+\left(264-260\right)+...+\left(216-212\right)+\left(208-204\right)+\)\(\left(200-196\right)\)

\(=4+4+4+4+4+4+4+4+4+4+4=44\)

Cảm ơn bạn nha

(dấu . là dấu nhân )

a, \(\frac{3}{2}\cdot\frac{4}{7}+\frac{3}{7}\cdot\frac{3}{2}\)

= \(\frac{3}{2}\left(\frac{4}{7}+\frac{3}{7}\right)\)

=\(\frac{3}{2}\cdot\frac{7}{7}=\frac{3}{2}\)

b, \(\frac{12}{5}\cdot4-4\cdot\frac{7}{5}\)

=\(4\left(\frac{12}{5}-\frac{7}{5}\right)=4\cdot\frac{5}{5}=4\)

c, \(\frac{5}{11}:\frac{1}{2}+\frac{6}{11}:\frac{1}{2}\)

=\(2\left(\frac{5}{11}+\frac{6}{11}\right)=2\cdot\frac{11}{11}=2\)

a;3/2x(4/7+3/7)

=3/2x1

=3/2

b;12/5x4-4x7/5

=4x(12/5-7/5)

=4x1

=4

c;5/11:1/2+6/11:1/2

=1/2:(5/11+6/11)

=1/2:1

=1/2

a) 3/2 * 4/7 +3/7 * 3/2

= 3/2*(4/7+3/7)

= 3/2*1

=3/2

b) 12/5 * 4 -4*7/5

=4*(12/5-7/5)

= 4*1

=4

c) 5/11 :1/2 + 6/11 : 1/2

=1/2 : (5/11 +6/11)

=1/2 : 1

=1/2

a) (n+3) Chia hết cho (n-1)

Ta có : (n+3)=(n-1)+4

Vì (n-1) chia hết cho (n-1) 

Nên (n+3) chia hết cho (n-1) thì 4 chia hết cho (n-1)

=> n-1 thuộc Ư(4)={1;2;4}

n-1     1          2             4

n         2          3            5

Vậy n thuộc {2;3;5 } thì (n+3) chia hết cho (n-1)

b)(4n+3) chia hết cho (2n+1)

Ta có : (4n+3)=2n.2+1+2

Vì (2n+1) chia hết cho (2n+1)

Nên (4n+3) chia hết cho (2n+1) thì 3 chia hết cho (2n+1)

=> 2n+1 thuộc Ư(3)={1;3}

2n+1                 1              3 

2n                    0               2

n                      0              1

Vậy n thuộc {0;1} thì (4n+3) chia hết cho (2n+1)

a)B = ( 2 + 4 + 6 + 8 +........+ 2014 ) - ( 3 + 5 + 7 + 9 +.......+ 2011 )

= 1015056 - 1012035

= 3021

Mk nhanh nhất đó 

Cảm ơn nha nguyen thi lan huong

3021

ai tk mk

mk tk lại

mk hứa

yên tâm

thank nhiều

=1 NHE BAN

= 1 nhé 

Tk đi mà.................Thanks

a>2 suy ra a-2>0

b>2 suy ra b-2>0

suy ra (a-2)(b-2)=ab-2a-2a+4>0

suy ra ab+4>2(a+b)

ta có a.b>2.2=4 suy ra ab+ab>ab+4>2a+2b

suy ra 2ab>2(a+b)

suy ra ab>a+b

suy ra bạn viết dấu nhé đừng viết chữ như mình

 CHÚC BẠN HỌC TỐT 

a) \(E=|3x-7|+|3x+2|+8\)

\(E=|7-3x|+|3x+2|+8\)

Do : \(|a|\ge a\)

\(\Rightarrow E_{min}\text{=}7-3x+3x+2+8\)

\(\Rightarrow E_{min}\text{=}17\)

Dấu '' = '' xảy ra : \(\Leftrightarrow\dfrac{-2}{3}\le x\le\dfrac{7}{3}\)