1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 

= ( 1 + 9) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + 10 + 5 

=    10     +    10      +     10     +   10        + 10   + 5

=    55 k minh nha

= (1 + 9) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + 5 + 10

= 10 + 10 + 10 + 10 + 5 + 10

= 55

k tớ nhé

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

=(1+9)+(2+8)+(3+7)+(4+6)+5+10

=10+10+10+10+10+5

=55

`a,MSC:45`

`7/9=(7xx5)/(9xx5)=35/45`

`2/5=(2xx9)/(5xx9)=18/35`

`b,MSC:21`

`6/7=(6xx3)/(7xx3)=18/21`

`17/21` giữ nguyên

`c,MSC:36`

`2/3=(2xx12)/(3xx12)=24/36`

`1/4=(1xx9)/(4xx9)=9/36`

`5/9=(5xx4)/(9xx4)=20/36`

\(a,\dfrac{7}{9}=\dfrac{7.5}{9.5}=\dfrac{35}{45}\\\dfrac{2}{5}=\dfrac{2.9}{5.9}=\dfrac{18}{45}\\ b,\dfrac{6}{7}=\dfrac{6.3}{7.3}=\dfrac{18}{21}\\ \dfrac{17}{21}giữnguyên\\ c,\dfrac{2}{3}=\dfrac{2.12}{3.12}=\dfrac{24}{36}\\ \dfrac{1}{4}=\dfrac{1.9}{4.9}=\dfrac{9}{36}\\ \dfrac{5}{9}=\dfrac{5.4}{9.4}=\dfrac{20}{36}\)

đợi mình xíu 

\(\frac{4^6.9^5+6^9.120}{8^4.3^{12}-6^{11}}\)

\(\Leftrightarrow\frac{\left(2^2\right)^6.\left(3^2\right)^5+\left(2.3\right)^9.2^3.3.5}{\left(2^3\right)^4.3^{12}-\left(2.3\right)^{11}}\)

\(\Leftrightarrow\frac{2^{12}.3^{10}+2^9.3^9.2^3.3.5}{\left(2^3\right)^4.3^{12}-\left(2.3\right)^{11}}\)

\(\Leftrightarrow\frac{2^{12}.3^{10}+2^9.3^9.2^3.3.5}{2^{13}.3^{13}-2^{11}.3^{11}}\)

\(\Leftrightarrow\frac{2^{12}.3^{10}+2^{12}.3^{10}.5}{2^{12}.2^{12}-2^{11}.2^{11}}\)

\(\Leftrightarrow\frac{2^{12}.3^{10}.\left(1+5\right)}{6^{12}-6^{11}}\)

\(\Leftrightarrow\frac{2^{12}.3^{10}.6}{6^{11}.\left(6-1\right)}\)

\(\Leftrightarrow\frac{2^{12}.3^{10}.2.3}{6^{11}.\left(6-1\right)}\)

\(\Leftrightarrow\frac{2^{13}.3^{11}}{6^{11}.5}\)

\(\Leftrightarrow\frac{2^{11}.3^{11}.2^2}{6^{11}.5}\)

\(\Leftrightarrow\frac{6^{11}.4}{6^{11}.5}\Leftrightarrow\frac{4}{5}\)

155 nha bn

155 nha bạn , k cho mình nha

1+2+3+4+5+6+7+8+9+10+100

=(1+9)+(2+8)+(3+7)+(4+6)+5+10+100

=10+10+10+10+5+10+100

=45+110

=155

Ta thấy :

1 x 2 = 2

2 x 3 = 6

3 x 4 = 12

4 x 5 = 20

5 x 6 = 30

6 x 7 = 42

...

Khoảng cách giữa các tích là một dãy số 4 ; 6 ; 8 ; 10 ; 12 ; ...

Áp dụng công thức tính số số hạng ra kết quả 330

330 nhé 

tk mình nha  Nguyễn Thanh Huyền

( 5/4x - 2/3 )^4 = 57/16 + 3/2

=> ( 5/4x - 2/3 )^4 = 81/16

=> ( 5/4x - 2/3 )^4 = 3^4/2^4

=> 5/4x - 2/3 = 3/2

=> 5/3x = 13/6

=> x = 13/10

      Vậy x = 13/10

\(\left(\frac{5}{4}x-\frac{2}{3}\right)^4-\frac{3}{2}=\frac{57}{16}\)

\(\left(\frac{5}{4}x-\frac{2}{3}\right)^4-\frac{3}{2}=\frac{57}{16}+\frac{3}{2}\)

\(\left(\frac{5}{4}x-\frac{2}{3}\right)=\frac{81}{16}\)

Ta xét 2th:

Th1: \(\frac{5}{4}x-\frac{2}{3}=\left(\frac{81}{16}\right)^{\frac{1}{4}}\)

\(\Rightarrow x=\frac{26}{15}\)

Th2: \(\frac{5}{4}x-\frac{2}{3}=-\left(\frac{81}{16}\right)^{\frac{1}{4}}\)

\(\Rightarrow x=-\frac{2}{3}\)

\(\Rightarrow\orbr{\begin{cases}x=\frac{26}{15}\\x=-\frac{2}{3}\end{cases}}\)

a)45

b)30

k mk đê

a. = 45

b, = 30

1+2+3+4+5+6+7+8+9=45

2+4+6+8+10=30

hok tốt

Xin cảm ơn.!^_^

Bằng:1202339.043

1203792.304

?!

:))

Spam ko zui đâu cj:)