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a: \(=\dfrac{-28}{36}+\dfrac{15}{36}-\dfrac{26}{36}=\dfrac{-39}{36}=\dfrac{-13}{12}\)
b: \(=\dfrac{11}{9}\left(\dfrac{15}{4}-\dfrac{7}{4}-\dfrac{5}{4}\right)=\dfrac{11}{9}\cdot\dfrac{3}{4}=\dfrac{11}{12}\)
c: \(=15+\dfrac{9}{7}+6+\dfrac{2}{3}-5-\dfrac{5}{9}\)
\(=16+\dfrac{88}{63}=\dfrac{1096}{63}\)
d: \(=\dfrac{5}{6}-\dfrac{1}{3}+\dfrac{2}{18}\)
\(=\dfrac{15-6+2}{18}=\dfrac{11}{18}\)
Đề răng dài thế này thì tui giải từng câu hí
a) \(\dfrac{-7}{9}+\dfrac{5}{12}-\dfrac{13}{18}\left(MSC:36\right)\)
\(=\dfrac{-28}{36}+\dfrac{15}{36}-\dfrac{26}{36}\)
\(=\dfrac{-13}{36}-\dfrac{26}{36}\)
\(=\dfrac{-39}{36}\)
\(=\dfrac{13}{3}\)
b) \(\dfrac{11}{9}.\dfrac{15}{4}-\dfrac{11}{4}.\dfrac{7}{9}-\dfrac{11}{9}.\dfrac{5}{4}\)
\(=\left(\dfrac{15}{4}-\dfrac{11}{4}-\dfrac{5}{4}\right).\dfrac{11}{9}\)
\(=\left(1-\dfrac{5}{4}\right).\dfrac{11}{9}\)
\(=\left(\dfrac{4}{4}-\dfrac{5}{4}\right).\dfrac{11}{9}\)
\(=\dfrac{-1}{4}.\dfrac{11}{9}\)
\(=\dfrac{-11}{36}\)
Các bạn ơi,mình ghi thiếu,còn 3 câu nữa nha!!!~~nya
e)| \(\dfrac{5}{2}\)x-\(\dfrac{1}{2}\) |-(-22).\(\dfrac{1}{3}\)(0,75-\(\dfrac{1}{7}\))=\(\dfrac{-5}{13}\):2\(\dfrac{9}{13}\)-0,5.(\(\dfrac{-2}{3}\))
f)| 5x+21 | = | 2x -63 |
g) -45 - |-3x-96 | - 54=-207
Làm ơn giúp mình với ạ!Mình đang cần gấp lắm trong ngày hôm nay ạ!!!Mình xin cảm ơn các bạn nhiều nhiều lắm luôn đó!!!Thank you very much!!!(^-^)
a, (\(\dfrac{2}{9}\)(6x - \(\dfrac{3}{4}\)) - 3(\(\dfrac{1}{4}x-\dfrac{1}{5}\)) = \(\dfrac{-8}{15}\)
<=> (\(\dfrac{4}{3}x-\dfrac{1}{6}\)) - (\(\dfrac{3}{4}x-\dfrac{3}{5}\)) = \(\dfrac{-8}{15}\)
<=> \(\dfrac{4}{3}x-\dfrac{1}{6}-\dfrac{3}{4}x+\dfrac{3}{5}=\dfrac{-8}{15}\)
<=> \(\dfrac{7}{12}x+\dfrac{13}{30}=\dfrac{-8}{15}\)
<=> \(\dfrac{7}{12}x=\dfrac{-8}{15}-\dfrac{13}{30}\)
<=> \(\dfrac{7}{12}x=-\dfrac{29}{30}\)
<=> x = \(-\dfrac{58}{35}\)
@Nguyễn Gia Hân
1/A=1.21.22.23.24.25 câu 2 làm tương tự
A.2=2.22.23.24.25.26
A.2-A=(2.22.23.24.25.2 mũ 6)-(1.21.22.23.24.25)
A=26-1
3 A=1+3+32+33+...37
3.A=3+32+33+34...+38
2A=38-1
A=(38-1):2
2) Tinh nhanh:
a) \(\dfrac{5}{23}\) . \(\dfrac{17}{26}\) + \(\dfrac{5}{23}\) . \(\dfrac{10}{26}\) - \(\dfrac{5}{23}\)
= \(\dfrac{5}{23}\) . \(\left(\dfrac{17}{26}+\dfrac{10}{26}-1\right)\)
= \(\dfrac{5}{23}\) . \(\left(\dfrac{27}{26}-1\right)\) = \(\dfrac{5}{23}\) . \(\dfrac{1}{26}\)
= \(\dfrac{5}{598}\)
b) \(\dfrac{1}{7}.\dfrac{5}{9}+\dfrac{5}{9}.\dfrac{2}{7}+\dfrac{5}{9}.\dfrac{1}{7}+\dfrac{5}{9}.\dfrac{3}{7}\)
= \(\dfrac{5}{9}.\left(\dfrac{1}{7}+\dfrac{2}{7}+\dfrac{1}{7}+\dfrac{3}{7}\right)\)
= \(\dfrac{5}{9}\) . 1= \(\dfrac{5}{9}\)
Ta có :
A = 2 + 2 2 + 2 3 + 2 4 + 2 5 + 2 6 + 2 7 + 2 8 + 2 9 + 2 10 + 2 11 + 2 12
= ( 2 + 2 2 ) + ( 2 3 + 2 4 ) + ( 2 5 + 2 6 ) + ( 2 7 + 2 8 ) + ( 2 9 + 2 10 ) + ( 2 11 + 2 12 )
= 2 ( 1 + 2 ) + 2 3 ( 1 + 2 ) + 2 5 ( 1 + 2 ) + 2 7 (1 + 2 ) + 2 9 (1 + 2 ) + 2 11 ( 1 + 2 )
= 2 .3 + 2 3 .3 + 2 5 .3 + 2 7 .3 + 2 9 .3 + 2 11 .3
= ( 2 + 2 3 + 2 5 + 2 7 + 2 9 + 2 11 ).3 chia hết cho 3
Ta lại có :
A = 2 + 2 2 + 2 3 + 2 4 + 2 5 + 2 6 + 2 7 + 2 8 + 2 9 + 2 10 + 2 11 + 2 12
= ( 2 + 2 2 + 2 3 ) + ( 2 4 + 2 5 + 2 6 ) + ( 2 7 + 2 8 + 2 9 ) + ( 2 10 + 2 11 + 2 12 )
= 2 ( 1 + 2 + 2 2 ) + 2 4 ( 1 + 2 + 2 2 ) + 2 7 (1 + 2 + 2 2 ) + 2 10 ( 1 + 2 + 2 2)
= 2 .7 + 2 4 .7 + 2 7 .7 + 2 10 .7
= ( 2 + 2 4 + 2 7 + 2 10 ).7 chia hết cho 7
Ta lại có :
A = 2 + 2 2 + 2 3 + 2 4 + 2 5 + 2 6 + 2 7 + 2 8 + 2 9 + 2 10 + 2 11 + 2 12
= ( 2 + 2 2 + 2 3 + 2 4 ) + ( 2 5 + 2 6 + 2 7 + 2 8 ) + ( 2 9 + 2 10 + 2 11 + 2 12 )
= 2 ( 1 + 2 + 2 2 + 2 3 ) + 2 5 ( 1 + 2 + 2 2 + 2 3) + 2 9 (1 + 2 + 2 2 + 2 3)
= 2 .15 + 2 5 .15 + 2 9 .15
= ( 2 + 2 5 + 2 9 ). 15 chia hết cho 5 ( vì 15 chia hết cho 5 )
ta có
\(A=1+2+2^2+2^3+2^4+..+2^{10}+2^{11}\)
\(\Leftrightarrow A=\left(1+2^3\right)+\left(2+2^4\right)+\left(2^2+2^5\right)+\left(2^6+2^9\right)+\left(2^7+2^{10}\right)+\left(2^8+2^{11}\right)\)
\(\Leftrightarrow A=\left(1+2^3\right)\left(1+2+2^2+2^6+2^7+2^8\right)=9\cdot\left(1+2+2^2+2^6+2^7+2^8\right)\)
Vì vậy A chia hết cho 9