= 2589

tk nha

861+732+367+203+426=2589 nha  cong chua ichigo !

=2589 nha bạn

S = 1.2 + 2.3 + 3.4 + ... + 39.40

3S = 1.2.3 + 2.3.3 + 3.4.3 + ... + 39.40.3

3S = 1.2.(3-0) + 2.3.(4-1) + ... + 39.40.(41-38)

3S = 1.2.3 - 0.1.2 + 2.3.4 - 1.2.3 +...+ 39.40.41 - 38.39.40

3S = 39.40.41

S = 39.40.41 : 3

S = 21320

Đáp án là :

a = 5 và b = 7

Phép tính là : 

57 x 75 = 4275

Vậy ab : 57

k cho tớ nha bn

\(36\times x-x=203\times20\\ \Rightarrow\left(36-1\right)\times x=4060\\ \Rightarrow35\times x=4060\\ \Rightarrow x=4060:35\\ \Rightarrow x=116\)

b)\(\frac{28}{100}x+\frac{4}{25}+\frac{10}{4}=\frac{203}{50}\)

<=>\(\frac{28}{100}x=\frac{203}{50}-\frac{10}{4}-\frac{4}{25}=\frac{406-250-16}{100}\)

<=>\(\frac{28}{100}x=\frac{140}{100}\)

<=>\(x=\frac{140}{100}:\frac{28}{100}=\frac{140}{100}.\frac{100}{28}\)

<=>x=5

a) \(\frac{1}{2}x+\frac{9}{4}-\frac{8}{20}=\frac{77}{20}\)

=>  \(\frac{1}{2}x=\frac{77}{20}+\frac{8}{20}-\frac{9}{4}=2\)

=>  \(\frac{x}{2}=2\Rightarrow x=2\cdot2=4\)

vậy x = 4

b) \(\frac{28}{100}x+\frac{4}{25}+\frac{10}{4}=\frac{203}{50}\)

=>  \(\frac{28}{100}x=\frac{203}{50}-\frac{10}{4}-\frac{4}{25}=1\frac{2}{5}=\frac{7}{5}\)

=> \(\frac{28x}{100}=\frac{7}{5}\Rightarrow28x=\frac{100\cdot7}{5}=140\Rightarrow x=140:28=5\)

vậy x = 5

c)  \(\frac{100}{58}=\frac{1}{2}x\)

=>  \(\frac{100}{58}=\frac{x}{2}\Rightarrow x=\frac{100\cdot2}{58}=3\frac{13}{29}=\frac{100}{29}\)

vậy x = 100/29

ACD =Đ

C=S

x+4=20³:20
x+4=20²
x+4=400
x    = 400-4
x    = 396
 

x+4=20^3÷20

x+4=8.000÷20

x+4=400

x     =400-4

x     =396

Vậy x=396

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