day la toan tinh nhanh day

`a)125+214+316`

125 lẻ;214 chẵn;316 chẵn

`=>125+214+316` lẻ nên không chia hết cho 2

`b)136+348+165+17`

136 chẵn;348 chẵn;165 lẻ;17 lẻ

`=>136+348+165+17` chẵn nên chia hết cho 2

a) Ta có:

\(\left\{{}\begin{matrix}125⋮̸2\\214⋮2\\316⋮2\end{matrix}\right.\)\(\Rightarrow125+214+316⋮̸2\)

b) Ta có:

\(\left\{{}\begin{matrix}136⋮2\\348⋮2\\165⋮̸2\\17⋮̸2\end{matrix}\right.\)\(\Rightarrow136+348+165+17⋮2\)

b) 136 . (-47) +136 . (-304)

= 136 . [(-47) + (-304)]

= 136. (-351) = -47736

c) (-48) .72 +36 . (-304)

= (-48).72 + 72 . (-152)

= 72. [(-48) + (-152)]

= 72. (-200) = -14400

=34000+354

=34354

34000+354

=34354

Bài 1 . Thực hiện phép tính :

a, ( 11 + 159 ) . 37 + ( 185 - 31 ) : 14

= 170 . 37 + 154 : 14

= 6290 + 11

= 6301

b, [ 25 . 103 + 7225 : 17 - ( 1500 - 125 ) : 5 ] . 32

= [ 25 . 103 + 7225 : 17 - 1375 : 5 ] . 32

= [ 2575 + 425 - 275 ] . 32

= 2725 . 32

= 87200

c, 136 . 25 + 75 . 136 - 6² . 10²

= 136 . ( 25 + 75 ) - 36 . 100

= 136 . 100 - 36 . 100

= 100 . ( 136 - 36 )

= 100 . 100

= 10000

a, (11+159).37+(185-31):14 b,[25.103+7225:17-(1500-125):5].32 c, 136.25+75.136 - 6².10²

=170.37+154:14 =[2575+425-1375:5].32 =136.(25+75)- (6.10)²

=6290+11 =[2575+425-275].32 =136.100 - 60²

=6301 =2725.32 =13600 - 3600

= 87200 =10000

Câu 2: 

Gọi hai só chẵn liên tiếp là 2k+2;2k+4

Theo đề, ta có: \(A=\left(2k+2\right)\left(2k+4\right)=4\left(k+1\right)\left(k+2\right)\)

Vì k+1 và k+2 là hai số lien tiếp

nên (k+1)(k+2) chia hết cho 2 

=>A chia hết cho 8

a: \(A=\left(\frac{136}{15}-\frac{28}{5}+\frac{62}{10}\right)\cdot\frac{21}{24}\)

\(=\left(\frac{272}{30}-\frac{168}{30}+\frac{186}{30}\right)\cdot\frac78\)

\(=\frac{290}{30}\cdot\frac78=\frac{29}{3}\cdot\frac78=\frac{203}{24}\)

b: \(B=\frac56+6\frac56\left(11\frac{5}{20}-9\frac14\right):8\frac13\)

\(=\frac56+\frac{41}{6}\cdot\left(11+\frac14-9-\frac14\right):\frac{25}{3}=\frac56+\frac{41}{6}\cdot2\cdot\frac{3}{25}\)

\(=\frac56+\frac{41}{25}=\frac{125}{150}+\frac{246}{150}=\frac{371}{150}\)

c: \(C=1+3+6+\cdots+1225\)

\(=\frac12\left(2+6+12+\cdots+2450\right)=\frac12\cdot\left(1\cdot2+2\cdot3+\cdots+49\cdot50\right)\)

\(=\frac12\cdot\left\lbrack1\left(1+1\right)+2\left(2+1\right)+\cdots+49\left(49+1\right)\right\rbrack=\frac12\cdot\left\lbrack\left(1+2+\cdots+49\right)+\left(1^2+2^2+\cdots+49^2\right)\right\rbrack\)

\(=\frac12\cdot\left\lbrack49\cdot\frac{50}{2}+\frac{49\left(49+1\right)\left(2\cdot49+1\right)}{6}\right\rbrack\)

\(=\frac12\cdot\left\lbrack49\cdot25+49\cdot50\cdot\frac{99}{6}\right\rbrack=\frac12\cdot\left\lbrack49\cdot25+49\cdot25\cdot33\right\rbrack=\frac12\cdot49\cdot25\cdot\left(33+1\right)\)

\(=49\cdot25\cdot\frac{34}{2}=49\cdot25\cdot17=20825\)