ngu câu này mà ko biết 

no no no

236 + 476 + 449 + 864 + 167 + 437 - 253 - 643 - 476 - 578 + 234 = 476 

~học tốt~

bằng 1 số nào đó

a, (y-476)x2=2196x3
(y-476)x2=2196x2+2196
(y-476)x2-2196x2=2196
(y-476-2196)x2=2196
(y-(476+2196)x2=2196
(y-2672)x2=2196
(y-2672)x2=1098x2
(y-2672)x2-1098x2=0
(y-2672-1098)x2=0
(y-(2672+1098)x2=0
(y-3770)x2=0
y-3770=0
y=3770
ĐS: y=3770

Tính bằng 2 cách :

a). 234 x 25 + 234 x 75 

C1: \(234\times25+234\times75\)

\(=5850+17550\)

\(=23400\)

C2: \(234\times25+234\times75\)

\(=234\times\left(25+75\right)\)

\(=234\times100\)

\(=23400\)

b). 765 x 123 - 755 x 23

C1: \(765\times123-765\times23\)

\(=94095-17595\)

\(=76500\)

C2: \(765\times123-765\times23\)

\(=765\times\left(123-23\right)\)

\(=765\times100\)

\(=76500\)

=> Bạn xem lại đề ạ!

c). 476 x ( 45 + 55 )

C1: \(476\times\left(45+55\right)\)

\(=476\times100\)

\(=47600\)

C2: \(476\times\left(45+55\right)\)

\(=476\times45+476\times55\)

\(=21420+26180\)

\(=47600\)

d). 2415 : 5 : 5

=> Xem lại đề ạ

e). ( 76 x 28 ) : 7

C1: \(\left(76\times28\right)\div7\)

\(=2128\div7\)

\(=304\)

C2: \(\left(76\times28\right)\div7\)

\(=76\times\left(28\div7\right)\)

\(=76\times4\)

\(=304\)

g). ( 175 + 29070 ) : 5

C1: \(\left(175+29070\right)\div5\)

\(=29245\div5\)

\(=5849\)

C2: \(\left(175+29070\right)\div5\)

\(=175\div5+29070\div5\)

\(=35+5814\)

\(=5849\)

h). ( 3224 - 1236 ) : 4

C1: \(\left(3224-1236\right)\div4\)

\(=1988\div4\)

\(=497\)

C2: \(\left(3224-1236\right)\div4\)

\(=3224\div4-1236\div4\)

\(=806-309\)

\(=497\)

\(A=xx+yy=x^2+y^2\)

Áp dụng BĐT Cauchy-Schwarz ta có:

\(\left(1^2+1^2\right)\left(x^2+y^2\right)\ge\left(1\cdot x+1\cdot y\right)^2=4\)

\(\Rightarrow2\left(x^2+y^2\right)\ge4\)

\(\Rightarrow A\ge2\)

Dấu "=" xảy ra khi \(\left\{\begin{matrix}x+y=2\\x=y\end{matrix}\right.\)\(\Rightarrow x=y=1\)

=> 90 * 100 *x  = 90 * 130

=> 9000 * x = 11700

=> x= 1,3

1,3

tick nha Hatake Kakashi

(x+2988)x2-1567 =4435

(x+2988)x2=4435+1567

(x+2988)x2=6002

x+2988=6002:2

x+2988=3001

x=3001-2988

x=13

(x + 2988) x 2 - 1567 = 4435  

(4435+1567):2=x+2988

6002:2=x+2988

3001=x+2988

x=3001-2988

x=13

(x + 2988) x 2 - 1567 = 4435  

(4435+1567):2=x+2988

6002:2=x+2988

3001=x+2988

x=3001-2988

x=13

476 x 476 + 523 x 476 + 476 = 476 x ( 476 + 523 + 1 ) = 476 x 1000 = 476000

\(=476\times476+523\times476+1\times476\)

\(=\left(476+523+1\right)\times476\)

\(=1000\times476\)

\(=476000\)

= 476 x 476 + 523 x 476 + 476 x 1

= 476 x (523 + 476 + 1 )

= 476 x 1000

= 476000

Chọn B